The presence of supportive relationships has important implications for athletes’ development, well-being, and performance. In particular, the perception that support is available if needed is generally more strongly and consistently associated with favorable outcomes compared to the actual receipt of support. This chapter reviews these different types of social support and evidence of their impact in sport. Particular emphasis is placed on how social support influences and interacts with stress, appraisals, and coping, along with theories that explain these processes. By examining contemporary literature, the chapter also highlights applied implications for athletes and their support personnel to help optimize supportive environments for well-being and performance. Future research directions are discussed including the need to examine the effects of multiple types of support concurrently, how support is provided, and the provider’s perspective.