Trimethoprim-sulfamethoxazole (TMP/SMX) is a widely prescribed antimicrobial for the management of several uncomplicated infections. It is commonly used for the treatment and prophylaxis of Pneumocystis jirovecii pneumonia (PCP) in the HIV-infected population. The adverse reaction to TMP/SMX is more frequent and severe in HIV-infected patients as compared to the general population. Here, we report a case of Stevens-Johnson syndrome (SJS) secondary to TMP/SMX. The patient had a generalized cutaneous reaction with involvement of the eyes, oral cavity, and genitals. He had elevated hepatic alanine aminotransferase and aspartate aminotransferase enzyme. TMP/SMX therapy was stopped and supportive treatment was started. His condition improved after eight days of stopping TMP/SMX therapy.