BACKGROUND AND SETTING: Because data on the determinants of the HIV care continuum from key populations such as men who have sex with men (MSM) in resource-limited settings are limited, the study aimed to characterize HIV care continuum outcomes and assess individual and network barriers to progression through the HIV care continuum among MSM in Abuja and Lagos, Nigeria. METHODS: TRUST/RV368 study used respondent-driven sampling to accrue MSM into community-based clinics in Nigeria. Participants received HIV testing at enrollment. HIV-infected participants were offered antiretroviral therapy (ART) with HIV RNA testing every 3 months (Abuja) or 6 months (Lagos). Multiple logistic regression models were used to calculate adjusted odds ratios for factors associated with each point in the HIV care continuum, including HIV testing, ART initiation, and 6-month viral suppression. RESULTS: A total of 1506 MSM were recruited, 1178 (78.2%) tested for HIV and 369 (31.3%) were HIV positive newly diagnosed. Of these, 188 (50.1%) initiated ART, 136 (72.3%) completed 6 months, and 96 (70.6%) were virally suppressed. Larger network size and stronger social network support were each positively associated with HIV testing uptake. Factors associated with ART initiation were higher education and stronger social network support. Having stronger social network support was associated with increased odds of viral suppression at 6 months. CONCLUSIONS: Social determinants of health potentiated increased HIV care continuum outcomes. Integration of HIV prevention, HIV counseling and testing services, and universal coverage of ART into a community-based clinic is critical in achieving better HIV care continuum outcomes.