We evaluated the efficacy of a sexual risk reduction intervention utilizing protection motivation and social cognitive theories to address knowledge, threat and coping appraisals, and condom use intentions among HIV-positive individuals in Nepal. Using a quasi-experimental research design, we assigned 277 participants to intervention (n=146) and control (n=131) groups. The intervention group received six sessions on sexual risk reduction strategies and the control group six sessions on medication adherence, smoking, and mental health. Data were collected at baseline and immediately after the intervention. Results indicate that the sexual risk reduction intervention produced a significant increase in HIV transmission knowledge, perceived threat and coping appraisals, and intentions to use condoms with regular, HIV-positive, and HIV-negative partners. The positive effects of the intervention remained significant after adjusting for baseline scores and other potential confounders. In conclusion, our theory-based sexual risk reduction intervention was effective in improving HIV transmission knowledge, perceived threat and coping appraisals, and condom use intentions. Further studies are needed to evaluate the long-term efficacy of the intervention in increasing protection motivation and maintaining preventive behaviors.