We examined the hypothesis that black and Latino men who have sex with men (MSM) who have supportive social relationships with other people are less likely to have unrecognized HIV infection compared with MSM of color who report lower levels of social support. We interviewed 1286 black and Latino MSM without known HIV infection in three metropolitan areas who were recruited using respondent driven sampling. Participants completed a computer-administered questionnaire and were tested for HIV. Unrecognized HIV infection was found in 118 men (9.2%). MSM who scored higher on the supportive relationship index had significantly lower odds of testing HIV-positive in the study. The mediation analysis identified two possible behavioral pathways that may partially explain this association: men who had strong supportive relationships were more likely to have had a test for HIV infection in the past 2 years and less likely to have recently engaged in high-risk sexual behavior. The findings illuminate the protective role of social relationships among MSM of color in our sample.