Despite the considerable prevalence of homelessness among very young children in the United States, there is a notable lack of research on risk, resilience, and developmental well-being of infants who experience family homelessness. In the present study, we considered social support as a resilience factor for quality of parent-infant relationships and parent depression among a sample of 106 parents and their infants (ages birth to 12 months) residing in emergency shelters for families experiencing homelessness. We assessed social support, parent histories of adverse experiences during childhood and adulthood, and parent current depression symptoms via structured interview measures, and we assessed quality of the parent-infant relationship with an observational approach. Results showed different patterns for the roles of adversity the parents had experienced during childhood compared to adversity experienced more recently, as adults. Childhood adversity predicted parent-infant responsiveness, with a positive association that was moderated by level of perceived social support. Parents with more childhood adversity showed more responsiveness with their infants only when they had access to high levels of social support. Adulthood adversity predicted higher scores for parent depression, while social support predicted lower parent depression scores. This work contributes to the very limited literature on the functioning of families with infants in shelters. Our discussion includes implications for research, policy, and prevention and intervention efforts.