Gynecomastia is an enlargement of breasts in men. This disease is commonly found in patients with impaired liver function and patients on additional hormonal use. Approximately, 10% to 25% of gynecomastia instances are attributed to the use of pharmaceutical substances. This study presented the case of a 41-year-old male patient with complaints of breast enlargement for 2.5 years before the examination. Breast enlargement was felt slowly without any period of shrinking, and no complaints of breast pain hardening, or nipple discharge. The patient was diagnosed with Auto Immune Deficiency Syndrome (AIDS) in 2009 and taking a Fixed-Dose Combination (FDC) of Anti-Retroviral Therapy (ART) with the composition of tenofovir, lamivudine, and efavirenz once a day. History of hormonal uses, other drugs, and alcohol consumption was denied. According to the physical examination, the patient had an adequate nutritional status, a BMI of 20.8 kg/m 2 , and enlargement of right and left breasts, the left breast was larger. According to the palpation, the enlarged breasts were firm and supple and there was no erosion or nipple discharge, or breast pain. The laboratory examination showed hepatitis marker, hormonal and thyroid levels are within normal limits. Medications are estimated to account for 10-25% of gynecomastia cases. Efavirenz decreases androgen activity through unknown factors. Several assumed mechanisms include the direct mammotropic effect of ARTs, and elevated IL-2 and IL-6 production due to T-helper cytokine response, thereby increasing the estrogen production which stimulates breast growth. Surgery can be done for cosmetic purposes.