Background: Benefits of buprenorphine-based opioid substitution therapy (OST) may be offset by its adverse effects on sexual functioning. Aim and objective: The aim of the article was to assess the prevalence and degrees of sexual dysfunction in sexually active males on buprenorphine-based OST for 6 months or longer. Materials and methods: Study participants were recruited from among the clients using the services at the Opioid Substitution Therapy Centre inside the premises of Silchar Medical College and Hospital. A semistructured questionnaire was used to collect sociodemographic data and to rule out the presence of symptoms of sexual dysfunction prior to initiation of OST. Two instruments, namely Arizona Sexual Experience Scale (ASEX) and International Index of Erectile Function (IIEF-15), were administered to evaluate the presence and degree of sexual dysfunction. Results: Fifty participants were enrolled in the test group and another 50 in the age-matched control group. Among the test participants, 52% had sexual dysfunction as per ASEX scale. As per IIEF-15, all but one of the test participants had some degree of erectile dysfunction (ED), with 6% having mild, 46% mild to moderate, 34% moderate, and 12% severe ED. None in the control group had sexual dysfunction as assessed by ASEX, while one among them had mild ED and the rest had no ED as per IIEF-15 scores. The test group showed significantly higher levels of dysfunction in all domains of sexual functioning measured by both the scales. No significant effect of age, current dose of buprenorphine, and duration of therapy was found on the prevalence or degree of sexual dysfunction. Conclusion: Different degrees of sexual dysfunction were highly prevalent in the participants making it imperative to routinely assess sexual functioning of the clients on buprenorphine-based OST and provide them with psychosexual counseling and necessary interventions whenever necessary.