Except for New Hampshire, all states and the District of Columbia require adult front-seat occupants of motor vehicles to use seat belts. Adult rear-seat passengers are also covered by the laws in 31 states and the District of Columbia. Children are covered by separate laws.

State seat belt laws are divided into two categories: primary and secondary. Primary seat belt laws allow law enforcement officers to stop a motor vehicle and to issue a ticket or citation to a driver or passenger for not wearing a seat belt without any other traffic offense having occurred. Secondary seat belt laws only allow law enforcement officers to issue a ticket or citation for not wearing a seat belt when there has been another traffic offense by an occupant of the vehicle for which the occupant may be issued a ticket or citation.

In Massachusetts, seat belt use is mandated by law under Massachusetts General Laws Chapter 90, Section 13A. The state has a primary seat belt law for front-seat occupants, meaning that law enforcement officers can stop and ticket a driver or front-seat passenger solely for not wearing a seat belt. The fine for an adult seat belt violation is $25 for each person not wearing a seat belt. Rear-seat passengers aged 16 and older are also required to wear seat belts, and this is enforced under a secondary law, which means that officers can only issue a ticket for not wearing a seat belt if the vehicle is stopped for another traffic violation. For children, Massachusetts has specific child passenger safety laws that require appropriate child safety seats or booster seats until the child is 8 years old or over 57 inches tall. Violation of these child safety laws can result in fines and fees that are significantly higher than those for adult seat belt violations.