In 2016, the Washington (State) Traffic Safety Commission partnered with the Confederated Tribes of the Colville Reservation to conduct an observational seat belt survey to establish a baseline estimate of seat belt use on the reservation. The same method for conducting the Washington State seat belt use estimate was tailored to the Colville Indian Reservation roadway network. Ninety sites on the reservation were randomly selected for observation, with 719 vehicles and 917 front seat occupants observed over a 2-week period in May. The baseline estimate for seat belt use on the Colville Indian Reservation is 64.1% (±7.0%). The seat belt use estimates varied at the four regions on the reservation. Similar to statewide results, nonstate routes had a lower seat belt use rate than state routes, and passenger vehicle pickup trucks had a lower rate than other vehicle types. Given the much lower seat belt use rate on the Colville Indian Reservation as compared with Washington State (64.1% versus 94.6%), effective countermeasures for increasing seat belt usage should be considered by the tribes.