Erroneous beliefs that it is toxic to drink alcohol while taking antiretroviral therapies (ART) used for treating HIV infection, known as alcohol interactive toxicity beliefs, may at least in part account for ART nonadherence among alcohol drinkers. This study was conducted to test a conceptual framework to explain the effects of interactive toxicity beliefs on ART adherence. Computerized surveys were administered to 124 participants receiving HIV care in the southeastern US. Serial mediation model with perceived sensitivity to medicines predicting HIV viral load through three mediating variables: alcohol-ART interactive toxicity beliefs, alcohol-ART avoidance behaviors, and ART adherence. HIV viral load extracted from medical records. Perceived sensitivity to medicines predicted HIV viral load; greater perceptions of medication sensitivity predicted lower HIV viral loads. In addition, there was a significant indirect effect of the serial chain of interactive toxicity beliefs → avoidance behaviors → ART adherence, indicating partial mediation of the relationship between perceived sensitivity to medicines and higher HIV viral load. Perceived sensitivity to medicines provides a conceptual basis for the effects of alcohol-medication interactive toxicity beliefs on ART adherence. Interactive toxicity beliefs are modifiable and can be altered to prevent intentional ART nonadherence.