You will usually see this phrase in an OSHA citation, inspection report, safety audit, or a letter stating that a hazard exposed workers to a risk of major injury. In that setting, a serious violation means a safety-law violation with a substantial probability of death or serious physical harm, and the employer knew or, with reasonable diligence, should have known about the condition. For private-sector workplaces, that definition comes from the federal Occupational Safety and Health Act, 29 U.S.C. § 666(k).

Practically, the label matters because it is more than a paperwork category. It signals that the hazard was not minor: falls, electrical exposure, struck-by risks, trench collapse, machine guarding failures, and similar conditions often qualify when the likely outcome is severe injury. A serious violation can trigger higher penalties, mandatory abatement, repeat scrutiny, and stronger evidence that the danger was foreseeable. It may also appear in disputes over wrongful termination, retaliation, or refusal to perform imminently dangerous work.

For an injury claim, a serious violation does not automatically prove negligence and does not by itself create a separate personal-injury lawsuit against an employer where workers' compensation is the exclusive remedy. But it can strongly support notice, causation, and breach arguments in a third-party case or other civil claim. In Massachusetts, the general deadline for filing a personal injury lawsuit is 3 years under G.L. c. 260, § 2A.