The House Ball Community (HBC) is an understudied network of African American men who have sex with men and transgender women, who join family-like houses that compete in elaborate balls in cities across the United States. From 2011 to 2012, we surveyed 274 recent attendees of balls in the San Francisco Bay Area, focusing on social networks, social support, and HIV-related behaviours. Participants with a high percentage of alters who were supportive of HIV testing were significantly more likely to have tested in the past six months (p = .02), and less likely to have engaged in unprotected anal intercourse (UAI) in the past three months (p = .003). Multivariate regression analyses of social network characteristics, and social support, revealed that testing in the past six months was significantly associated with social support for safer sex, instrumental social support, and age. Similarly, UAI in the past three months was significantly associated with social support for safer sex, homophily based on sexual identity and HIV status. HIV-related social support provided through the HBC networks was correlated with recent HIV testing and reduced UAI. Approaches utilising networks within alternative kinship systems, may increase HIV-related social support and improve HIV-related outcomes.