Neighborhood built environment features, including parks, may contribute to social capital, but these relationships have not been adequately explored in communities of color. Our study focused on a specific subset of this population—a national sample of diverse, low-income parents with young children (n = 1,611)—to assess relationships between social capital, parks (e.g., access, visit frequency, and satisfaction), and other aspects of the built environment (e.g., perceptions of neighborhood walkability, traffic, and crime). We found that park satisfaction (a measure of park quality) was strongly linked to social capital among low-income parents, but park use frequency and access (both related to park quantity) were not. Neighborhood walkability and safety from crime were also strong positive correlates of social capital. Despite social benefits of parks, moderate to low ratings of park satisfaction, neighborhood walkability, safety from crime, and social capital within our sample suggest that inequities in park and neighborhood quality may prevent families who might benefit the most from social capital (i.e., low-income minority populations) from enjoying key resources needed to cultivate it. Cities hoping to enhance social capital in vulnerable communities would be wise to invest in quality parks and built environment features that create opportunities for positive social interactions among low-income parents with young children.