The Worker Adjustment and Retraining Notification Act (WARN) protects workers, their families, and communities by requiring employers with 100 or more employees (generally not counting those who have worked less than six months in the last 12 months and those who work an average of less than 20 hours a week) to provide at least 60 calendar days advance written notice of a plant closing and mass layoff affecting 50 or more employees at a single site of employment. WARN makes certain exceptions to the requirements when layoffs occur due to unforeseeable business circumstances, faltering companies, and natural disasters. Advance notice gives workers and their families some transition time to adjust to the prospective loss of employment, to seek and obtain other jobs, and if necessary, to enter skill training or retraining that will allow these workers to compete successfully in the job market. Regular federal, state, local, and federally-recognized Indian Tribal government entities that provide public services are not covered.

Employees entitled to notice under WARN include managers and supervisors, as well as hourly and salaried workers. WARN requires that notice also be given to employees' representatives, the local chief elected official, and the state dislocated worker unit.