A seat belt buckle assembly, for quick release engagement with a mating tongue, has a latch mounted on a base for pivotal motion between a latching position, where the latch engages the tongue against withdrawal from the buckle assembly, and an unlatching position where the latch releases the tongue. A push button is also pivotally mounted on the base in an overlying relation to the latch. Interposed between the latch and the push button is a dual purpose spring capable of acting on both latch and push button for biasing the latch from the unlatching toward the latching position, and the push button away from the latch. For causing the latch to release the tongue, the push button is to be pushed manually against the force of the dual purpose spring, whereupon the push button acts directly on the latch for pivoting the same from the latching to the unlatching position against the force of the dual purpose spring. The buckle assembly may additionally include a pushout spring for throwing the tongue out of the buckle assembly when the tongue is unlatched.