Research is needed to identify culturally relevant factors that may contribute to sexual risk among African Americans. We investigated HIV-specific medical mistrust as one such cultural factor, often exhibited as conspiracy beliefs about HIV (e.g., "AIDS was produced in a government laboratory"), which may be indicative of general suspicion of HIV treatment and prevention messages. Over a 6-month time-period, we measured endorsement of HIV conspiracy beliefs three times and frequency of condom use monthly among 181 HIV-positive African American males. A hierarchical multivariate repeated-measures logistic random effects model indicated that greater belief in HIV conspiracies was associated with a higher likelihood of reporting unprotected intercourse across all time-points. An average of 54% of participants who endorsed conspiracies reported unprotected intercourse, versus 39% who did not endorse conspiracies. Secondary prevention interventions may need to address medical mistrust as a contributor to sexual risk among African Americans living with HIV.