Abstract Personal social networks profoundly influence a wide range of outcomes throughout the life course. But little research has considered how some features of individuals’ social networks may be shaped by experiences in early life. This study uses nationally representative data from the National Social Life, Health, and Aging Project to examine how childhood circumstances may shape the structure of older adults’ personal social networks. The analyses show that higher childhood socioeconomic status is associated with larger network size and a more expansive, less kin-based network structure. At the same time, higher levels of family happiness in childhood are associated with greater network density and more kin-centric network composition, which may reflect greater access to social support and overall network intimacy across the life course. The results suggest that studies of the relative advantages of social network structure may benefit from contextualizing individuals’ social networks in terms of their social origins. The article discusses the need for additional research on the life-course bases of the link between childhood circumstances and later-life network properties, and what role this connection plays in shaping later-life well-being.