Abstract Background The global COVID-19 pandemic has the potential to indirectly impact transmission dynamics and prevention of HIV and other sexually transmitted infections (STI). It is unknown what combined impact reductions in sexual activity and interruptions in HIV/STI services will have on HIV/STI epidemic trajectories. Methods We adapted a model of HIV, gonorrhea, and chlamydia for a population of approximately 103 000 men who have sex with men (MSM) in the Atlanta area. Model scenarios varied the timing, overlap, and relative extent of COVID-19–related sexual distancing and service interruption within 4 service categories (HIV screening, preexposure prophylaxis, antiretroviral therapy, and STI treatment). Results A 50% relative decrease in sexual partnerships and interruption of all clinical services, both lasting 18 months, would generally offset each other for HIV (total 5-year population impact for Atlanta MSM, −227 cases), but have net protective effect for STIs (−23 800 cases). If distancing lasted only 3 months but service interruption lasted 18 months, the total 5-year population impact would be an additional 890 HIV cases and 57 500 STI cases. Conclusions Immediate action to limit the impact of service interruptions is needed to address the indirect effects of the global COVID-19 pandemic on the HIV/STI epidemic.