Abstract: A seat belt adjuster which can be attached to the lap and shoulder belts of a conventional seat belt assembly so a passenger can adjust the positioning of the shoulder belt with respect to the passenger's upper torso. The seat belt adjuster includes a base and first and second pairs of flexible straps extending from the base. Each pair of straps can be interlocked to form first and second channels which slidably permit passage of the lap and shoulder belts therethrough. Each pair of straps can also be tighten to restrict the movement of the lap and shoulder belts through the first and second channels. In a preferred embodiment the first and second pair of straps are interlocked using Velcro strips. In an alternative embodiment a secondary locking loop, integral with one of the first or second pair of straps, is provided to strengthen the engagement of the first and second pairs of straps with the lap and shoulder belts.