Gay, bisexual, and other men who have sex with men (GBMSM) are associated with the widespread human immunodeficiency virus (HIV) transmission in Taiwan. Additionally, little is known about disclosure patterns and rates, as well as factors influencing disclosure, among GBMSM living with HIV in the country. HIV prevention for GBMSM is effective when HIV status is disclosed. For instance, GBMSM disclosing their HIV status can result in early pre-exposure prophylaxis with a serodiscordant partner. In this cross-sectional study of 200 GBMSM living with HIV conducted from June to November 2020, we assessed internalized homophobia (IHP Scale) and social support (Multidimensional Scale of Perceived Social Support), as well as self-reported disclosure and non-disclosure. Among the participants, 75.5% revealed their HIV status within 3 months of diagnosis. Younger age, occupation type, and number of sexual partners were some factors associated with disclosure. Those receiving more social support and who experienced less IHP were more likely to reveal their HIV status. On the contrary, older GBMSM and GBMSM living with HIV who worked in educational enterprises still experienced severe IHP. Policymakers and healthcare practitioners should be aware of the problems faced by GBMSM living with HIV and offer practical assistance to improve their mental health.