Background: Black sexual minority men and Black transgender women (BSMM/BTW) experience disproportionate levels of HIV/STI-related risk factors as well as police harassment (PH). PH is linked to psychiatric risk and could play a role in substance use, sexual risk behavior, and HIV/STI risk. Methods: We used data from the HIV Prevention Trials Network 061(HPTN 061) study to examine associations between PH and HIV/STI-related outcomes. Using PH exposure measured at baseline and 6-month study visits, we examined an ordinal exposure (PH reported at both visits, PH reported at either visit, versus PH reported at neither baseline nor 6 months) and a binary exposure of persistent PH reported at both visits (yes versus no). We estimate risk ratios (RR) for associations between PH and depression, use of alcohol and methamphetamine, multiple partnerships, condomless sex, and syphilis. Results: Persistent PH (binary) was associated with a 20% or greater increase in the risk of depression (RR, 1.26 (1.07, 1.47)) and multiple partnerships (RR, 1.20 (1.05, 1.39)). There was evidence that ordinal PH was associated with elevated risk of alcohol use (RR, 1.17 (1.00, 1.36)); the point estimate for the association between persistent PH and alcohol use was similar but the imprecision was greater (RR, 1.16 (0.95, 1.42)). Conclusion: PH may influence not only mental health but also behavioral risks that contribute to HIV/STI among BSMM/BTW, highlighting the potential wide-ranging and downstream effects of PH on health. Further research is required to confirm associations and elucidate pathways through which PH may influence HIV/STI among BSMM/BTW.