A co-worker backs a forklift into you, or drives the company van that you are riding in into a pole, or leaves a hazard that puts you in the hospital. Your medical bills mount, your wages stop, and workers’ compensation covers only part of what you have lost. So you ask the obvious question: can you sue the co-worker whose carelessness actually hurt you? In Massachusetts the answer usually turns on co-employee immunity — the rule that a fellow employee, acting within the course of the same employment, is generally shielded from a negligence lawsuit by the same workers’ compensation bargain that limits what you can recover from the employer.
That immunity is real, but it is not unlimited, and the exceptions are where many injured workers find a path to fuller recovery. A co-worker who was acting outside the scope of the common employment, or who injured you through an intentional act rather than ordinary carelessness, may not be protected at all. Whether the fellow-worker is immune or answerable turns on what they were actually doing when you were hurt — and that question is worth asking rather than assuming the comp system is the end of the road. The assumption that a co-worker is untouchable is exactly what leaves money on the table. Many workers accept comp and never learn a fuller recovery was possible. That quiet acceptance is what the reflexive immunity defense counts on. Asking the question changes the outcome more often than people expect. It costs nothing to ask and can be worth a great deal. Curiosity about the facts is the injured worker’s best asset here. The workers who recover the most are the ones who refuse to stop at the easy answer. Persistence, not luck, is what usually makes the difference. The claim that gets pursued is the claim that gets paid. An unfiled claim recovers nothing, however strong. Filing on time is the first and most basic protection. Everything else depends on the claim still being alive. A live claim can be developed; a lapsed one cannot. So the clock is the first thing to respect. Missing it forfeits everything else, no matter how strong the facts. Deadlines do not care about the merits. They only care whether you acted in time. Timeliness is the one thing no argument can fix later. So the calendar comes first, always. Only after the deadline is secured does the rest of the strategy unfold.
What follows is how this immunity works in Massachusetts: whether you can sue the co-worker who hurt you, the line between the common employment and a separate capacity, and how intentional torts by a co-worker fall outside the shield. This is general information, not advice about a specific case. Because the immunity is one piece of the larger question of when a workplace injury can go beyond comp, our discussion of when you can sue after a workplace injury is a natural companion to this one.
Can you sue the co-worker who hurt you?
The starting point is the workers’ compensation bargain, and how the courts have extended it from the employer to fellow employees.
The comp bargain and its exclusivity
Workers’ compensation is a trade-off: an injured worker gets benefits without having to prove fault, and in exchange gives up the right to sue the employer at common law for a work injury. Under Massachusetts General Laws chapter 152, section 23, accepting compensation releases the insurer and the employer from common-law claims arising from the injury, and under section 24 an employee who does not reserve the right to sue is held to have waived it. That exclusivity is the foundation of the whole system — the reason a hurt worker collects benefits but generally cannot bring a negligence suit against the employer. That trade is the backbone of the entire scheme.
How the shield reaches fellow employees
Massachusetts courts have extended that bargain to protect co-workers as well. The reasoning is that a fellow employee, acting within the course of the common employment, is carrying out the employer’s work, so allowing a negligence suit against that co-worker would undercut the exclusivity the statute created. As a result, when one employee negligently injures another and both are acting in the course of the same employment, the injured worker’s remedy is workers’ compensation, and a negligence action against the co-worker is generally barred. That is co-employee immunity in a sentence. Everything after that sentence is about where its edges fall. And the edges are where the interesting cases live. A rule with clear exceptions is only as strong as how those exceptions are applied. Applied carefully, the exceptions do real work for injured people. They are not technicalities; they are genuine paths to recovery. Each exception exists because the immunity, pushed too far, would be unjust. The law built in these escape valves on purpose. They are part of the design, not an afterthought. A system without them would be too harsh to be fair.
Why the rule exists
The policy behind the immunity is the same trade-off that drives the whole comp system: predictable, no-fault benefits in place of uncertain, fault-based lawsuits among the people who work side by side. Without it, ordinary workplace accidents would spawn negligence suits between co-workers, which the compensation bargain was designed to avoid. So the immunity is not an accident or a loophole; it is a deliberate feature of the system. Recognizing that helps focus the real question, which is not whether the immunity exists but whether the co-worker’s conduct falls inside or outside it. That is the question the rest of this piece is really about.
The common employment versus a separate capacity
The immunity protects a co-worker only while they are acting within the course of the common employment. Step outside that, and the shield can fall away.
Acting in the course of the common employment
The protection depends on the co-worker doing the employer’s work at the time. A co-employee performing job duties — operating equipment, driving for the job, carrying out an assigned task — who negligently injures a fellow worker is generally immune, because the conduct is part of the shared employment the comp bargain covers. The closer the co-worker’s act is to the ordinary work both were hired to do, the more firmly the immunity applies. Routine job tasks sit at the core of the protection. Move away from routine duties, and the protection starts to thin. The further the conduct drifts from the job, the weaker the shield becomes. At some point the co-worker is just another person who caused harm. And another person who caused harm can, in the right case, be answerable for it. The employment relationship is not a permanent force field. It protects certain conduct, in a certain context, and no more. Outside that context, ordinary tort principles return. And ordinary tort principles are far friendlier to the injured. They allow the full measure of damages the comp schedule withholds. That fuller measure is what makes the tort route worth pursuing. It is often the difference between partial and full compensation. And full compensation is what the injured person actually needs. Half a recovery still leaves real bills unpaid. The goal is to close that gap, not accept it. Closing it is what turns coverage into recovery. And recovery, not coverage alone, is the real objective. Everything in these cases bends toward that end. A recovery that makes the injured person whole is the measure of success.
The separate-capacity exception
But a co-worker does not carry immunity everywhere. When a fellow employee injures someone while acting in a capacity unrelated to the common employment — not doing the employer’s work, but acting on their own account — the reason for the immunity disappears, and a claim may be possible. The classic example is a co-worker who, off the clock or on a personal errand, negligently injures another; acting in that separate, personal capacity, the co-worker is not shielded the way an on-duty co-worker performing job tasks would be. The question is always whether the injuring conduct was part of the common employment or something the co-worker was doing outside it. That single question decides most of these disputes. It sounds simple, but the answer is buried in the facts. What looked like an on-duty accident sometimes turns out to be something else entirely. The first story about an incident is not always the accurate one. Initial reports are written quickly and often favor the employer. A closer look frequently tells a different story. The version that survives scrutiny is the one that counts.
Why the distinction is fact-specific
Because the line turns on what the co-worker was actually doing, these cases are intensely factual. Whether an act was within the course of the common employment or in a separate capacity depends on the details — the timing, the purpose, the relationship of the conduct to the job. That is why a reflexive assumption that “you can never sue a co-worker” is often wrong: the immunity is bounded by the common employment, and identifying conduct that falls outside it is exactly where a viable claim can appear. The edges of the immunity, not its center, are where cases are won. A careful reconstruction of the incident is what finds those edges. Nobody wins a co-worker case by conceding the immunity at the outset. You test it, and you make the other side prove it applies. The burden of establishing the immunity should not simply be handed over. Making the defense earn it is part of protecting the claim. Nothing about the immunity should be conceded for free. Every element of it is something the defense must actually establish. Assertion is not proof, and the burden matters.
Intentional torts by a co-worker
The other major limit on the immunity is the nature of the conduct. Co-employee immunity is built around negligence — the ordinary carelessness of shared work — and it does not extend to a co-worker’s deliberate wrongs.
Assault and intentional harm
When a co-worker intentionally injures you — an assault, a deliberate act meant to cause harm — that is not the kind of accidental, work-related negligence the compensation bargain was meant to absorb. An intentional tort is a personal wrong, and the immunity that protects a co-worker for careless job conduct does not shield a co-worker who deliberately attacks a fellow employee. In that situation a direct claim against the co-worker may be available even though the workplace is the setting. The setting does not convert a deliberate assault into a mere workplace accident. Intent changes the character of the act, and the law follows that change. A punch thrown in anger is not the same as a dropped tool. The law has always treated intent as a meaningful dividing line. Deliberate harm and careless harm are different in kind, not just degree. The comp bargain was written with that difference in mind. It was never meant to launder deliberate harm into a no-fault claim.
Why intentional conduct falls outside the bargain
The logic tracks the purpose of the immunity. The comp system trades tort suits for no-fault benefits because ordinary workplace accidents are an expected cost of doing business; a co-worker’s deliberate decision to harm someone is not. Treating an intentional assault as just another compensable workplace accident would stretch the bargain past its purpose. So the law draws a line between the negligent co-worker, who is generally immune, and the intentional wrongdoer, who is not. That line follows the purpose of the bargain rather than the location of the harm. Where the harm happened matters less than why and how. The compensation system absorbs accidents, not deliberate wrongs. That distinction is old, deliberate, and still decisive. It has survived because it reflects a basic sense of fairness. Deliberate wrongs belong in tort, not in the no-fault system. Keeping them there is what the intentional-tort exception does. It is a narrow exception, but an important one. Narrow does not mean unavailable in the right case. The right facts can bring even a narrow exception into play. And bringing it into play can change the whole outcome. One exception, well applied, can reopen a closed door. That is worth remembering before accepting that a door is shut.
The line between careless and deliberate
Because the immunity turns on this distinction, how the conduct is characterized matters enormously. Genuinely reckless or intentional conduct can fall outside the shield, while ordinary carelessness — even serious carelessness — usually does not. Sorting a given incident onto the right side of that line takes a careful look at what the co-worker actually did and intended, and it is often the difference between a barred claim and a live one. It is also why the label the employer or insurer puts on the incident should not be taken at face value. A convenient characterization is not the same as an accurate one. Insurers have every reason to call an incident routine negligence. Testing that label against the facts is part of the work. A label is a starting point for scrutiny, not a conclusion.
What co-employee immunity means for your claim
For an injured worker, the immunity shapes where compensation can come from — but it rarely leaves someone with nothing, and it does not touch everyone who might be responsible.
Comp still covers the injury
Even where a co-worker is immune, the workers’ compensation system still provides benefits for a work injury without any need to prove fault — medical treatment and wage replacement flow regardless of whether a lawsuit against the co-worker is possible. The immunity limits one avenue of recovery; it does not leave an injured worker uncovered. The first question is always whether the comp benefits themselves are being paid in full. A shortfall there is its own problem, separate from any lawsuit. Comp underpayment and a barred co-worker suit are two different fights. Both deserve attention, and neither should be assumed away. Assumptions are how recoverable claims quietly disappear. The most expensive mistake is assuming there is nothing to pursue. A short inquiry can prevent it. The cost of asking is low; the cost of not asking can be everything.
Third parties are not immune
Just as important, the immunity protects only fellow employees acting in the common employment — not outside parties. A negligent driver from another company, the manufacturer of a defective machine, a contractor from a different employer on the same site, or a property owner may all be liable in an ordinary third-party claim that runs alongside the comp case. Many workplace injuries involve exactly these outside parties, and identifying them can open a recovery the comp system alone does not provide. Those outside parties are where much of the real value often lies. A defective machine or a negligent outside driver carries no comp immunity. Finding them can transform what a case is worth. A single overlooked defendant can change the entire picture. Cases that looked like comp-only claims sometimes hold a substantial third-party suit. The search for that defendant is worth doing thoroughly. A rushed search misses exactly the parties that matter most. The most valuable defendant is often the one nobody thought to look for. Which is precisely why the search has to be deliberate. Deliberate searching is how hidden defendants surface.
When a co-worker claim is available
And where the co-worker’s conduct falls outside the immunity — a separate-capacity act, or an intentional tort — a direct claim against that co-worker may add another source of recovery. In those cases the injured worker can pursue full tort damages, including compensation for pain, suffering, and the lasting effects of the injury that workers’ compensation does not pay. In serious matters, including a catastrophic injury, the difference between comp alone and comp plus an available tort claim can be enormous. Tort damages reach losses that compensation simply does not. Pain, suffering, and full lost earning capacity fall outside the comp schedule. That gap is exactly what an available tort claim can fill. Filling it is often the whole point of looking past comp. Comp keeps the lights on; a tort claim can make an injured person whole. The two serve different purposes and can work together. Used together, they cover far more of the loss than either alone. Coordinating them is part of building the full recovery. A coordinated approach leaves less of the loss uncovered. Coverage of the whole loss is the goal worth aiming at. Anything less leaves the injured worker carrying part of it.
Protecting your claim against the immunity defense
Because the immunity is asserted almost reflexively, protecting a claim means testing whether it actually applies and pursuing every source of recovery the injury allows.
Testing whether the immunity really applies
The central task is examining what the co-worker was actually doing when you were hurt: were they carrying out the employer’s work within the common employment, or acting in a separate capacity, or acting intentionally? Those facts — not the insurer’s say-so — decide whether the shield applies. Developing the details of the incident, rather than accepting a blanket claim that a co-worker can never be sued, is what surfaces the cases that fall outside the immunity. The facts, not the slogan, control. “You can never sue a co-worker” is a slogan, not a legal rule. The legal rule has exceptions, and the exceptions have facts. And facts are things you investigate, not things you concede. Conceding the facts is conceding the case. Investigation is where barred claims turn into live ones. What the facts reveal is frequently better than what the label promised.
Finding every responsible party
Alongside that, the task is to identify everyone who may be liable beyond the immune co-worker — outside companies, equipment makers, other contractors, property owners — and to confirm the comp benefits are being paid correctly. Because third parties carry no comp immunity, a thorough look at who caused the injury frequently reveals a claim the compensation case does not, and preserving the evidence to support it matters from the start. Evidence of who did what fades quickly on a busy job site. Crews change, equipment is moved, and memories blur within weeks. Early preservation is often what keeps a claim alive. Waiting is the surest way to lose the proof you will need. Time favors the party that wants the claim to disappear. Acting early keeps the options open. Delay narrows them, sometimes permanently.
When to call a Boston injury lawyer
If a co-worker’s conduct caused your injury and you have been told workers’ compensation is your only option, it is worth testing that against the actual limits of the immunity — the separate-capacity and intentional-tort exceptions, and every non-employee who may share responsibility. A lawyer can determine whether the immunity truly applies, pursue any available claim against the co-worker or a third party, and make sure the comp benefits are correct; these cases are handled on contingency, so there is no fee unless there is a recovery. Our Boston personal injury attorneys handle workplace-injury and third-party claims across the Commonwealth and in nearby communities including Quincy and Cambridge, as reflected across our practice areas. If a co-worker hurt you, you can reach out to have every option evaluated.
Reviewed and Approved By
This article was reviewed for legal accuracy by Daniel J. Larson, the founding attorney of Larson Law and a Massachusetts-barred personal injury lawyer in Boston. He represents individuals and families harmed by negligence in serious-injury matters arising from motor-vehicle collisions, unsafe property conditions, and other preventable incidents. Attorney Larson works litigation-first, developing each case through detailed investigation, discovery, and expert analysis with the expectation that it may be tried. Before founding the firm, he defended doctors, hospitals, and other healthcare providers in malpractice litigation at a Boston firm — experience that informs how he anticipates the way insurers and defense counsel approach a claim. He is a member of the Massachusetts Bar Association and the Massachusetts Academy of Trial Attorneys.
Frequently asked questions
Can I sue a co-worker who caused my injury in Massachusetts?
Usually not for ordinary negligence, because of co-employee immunity. When a fellow employee negligently injures you while both of you are acting in the course of the same employment, your remedy is generally workers’ compensation, and a negligence suit against that co-worker is barred. But the immunity has limits: a co-worker acting outside the common employment, in a separate personal capacity, or one who injures you through an intentional act, may not be protected. Whether you can sue depends on what the co-worker was actually doing when you were hurt.
Why is a co-worker protected at all?
Because Massachusetts courts have extended the workers’ compensation bargain to fellow employees. The comp system gives injured workers no-fault benefits in exchange for giving up common-law suits over work injuries, and allowing negligence suits between co-workers doing the employer’s work would undercut that trade-off. So a co-worker performing job duties who carelessly injures a fellow employee is generally immune, with the injured worker’s remedy being compensation rather than a lawsuit.
What is the separate-capacity exception?
It is the idea that immunity protects a co-worker only while they are acting within the common employment. When a fellow employee injures you while acting in a capacity unrelated to the job — on a personal errand, off the clock, doing something outside the employer’s work — the reason for the immunity disappears, and a claim may be possible. The question is always whether the injuring conduct was part of the shared employment or something the co-worker was doing on their own account.
What if the co-worker hurt me on purpose?
An intentional tort generally falls outside the immunity. Co-employee immunity is built around the ordinary negligence of shared work, not a co-worker’s deliberate decision to harm someone. An assault or other intentional act is a personal wrong the compensation bargain was not designed to absorb, so a direct claim against a co-worker who intentionally injured you may be available even though it happened at work. How the conduct is characterized — careless versus deliberate — is central.
If the co-worker is immune, do I have any other options?
Yes. Workers’ compensation still covers the injury without proof of fault, and the immunity does not protect outside parties. A negligent driver from another company, the maker of a defective machine, a different employer’s contractor, or a property owner may be liable in a third-party claim that runs alongside your comp case. Identifying those non-employee parties often opens a recovery the compensation system alone does not provide, so it is worth looking beyond the immune co-worker.
Results Disclaimer: Past case results, settlements, and verdicts mentioned on this website do not guarantee or predict a similar outcome in any future case. Every case is unique and depends on its own facts and legal issues.