To identify factors - including social determinants of health (SDOH) - that explain racial/ethnic disparities in antiretroviral therapy (ART) adherence and sustained viral suppression (SVS) among U.S. men who have sex with men (MSM) with HIV. We used weighted data from 2017-2021 cycles of the Medical Monitoring Project. Among MSM taking ART, we calculated prevalence differences (PDs) with 95% confidence intervals (CIs) of ART adherence (100% ART adherence, past 30 days) and SVS (all viral loads in past 12 months <200 copies/ml or undetectable) for Black MSM (BMSM) and Hispanic/Latino MSM (HMSM) compared with White MSM (WMSM). Using forward stepwise selection, we calculated adjusted PDs with 95% CIs to examine if controlling for selected variables reduced PDs. After adjusting for age, any unmet service need, federal poverty level (FPL), food insecurity, homelessness, time since HIV diagnosis, gap in health coverage, and education, the BMSM/WMSM PD for ART adherence reduced from -16.9 to -8.2 (51.5%). For SVS, the BMSM/WMSM PD reduced from -8.3 to -3.6 (56.6%) after adjusting for ART adherence, age, homelessness, food insecurity, gap in health coverage, FPL, any unmet service need, time since diagnosis, and ER visit(s). The HMSM/WMSM PD for ART adherence reduced from -9.3 to -2.9 (68.8%) after adjusting for age and FPL. The unadjusted HMSM/WMSM PD for SVS was not statistically significant. Adjusting for SDOH and other factors greatly reduced racial/ethnic disparities in ART adherence and SVS. Addressing these factors - particularly among BMSM - could substantially improve health equity among MSM with HIV.