To describe social support patterns of gay and bisexual men with prostate cancer (GBMPCa) and how social support is associated with prostate cancer outcomes. A cross-sectional online survey with 186 GBMPCa recruited from a national cancer support group network. Descriptive statistics of social support and linear regression of social support on general and prostate cancer-specific quality of life (QOL). Social support and health-related QOL were assessed generally and specific to prostate cancer. Participants primarily relied on partners or husbands, gay and bisexual friends, chosen family, and men from support groups for support. The most common types of support received were informational and emotional social support. Low general social support was significantly associated with worse prostate cancer symptom bother and general mental QOL. Wanting more social support was significantly associated with worse prostate cancer-specific and general QOL. Clinicians should be aware of the different social support networks and needs of GBMPCa and refer them to relevant support groups to improve QOL.