Heat spreaders for use in semiconductor device testing, such as burn-in testing, are disclosed herein. In one embodiment, a heat spreader is configured to be coupled to a burn-in testing board including a plurality of sockets. The heat spreader includes (i) a frame having a plurality of apertures, and (ii) a plurality of heat sinks movably positioned within corresponding ones of the apertures. When the heat spreader is coupled to the burn-in testing board, the heat sinks are configured to extend into corresponding ones of the sockets to thermally contact semiconductor devices positioned within the sockets. The heat spreader can promote a uniform temperature gradient across the burn-in board during testing of the semiconductor devices.