Background: Peer support groups play a crucial role in enhancing the psychosocial well-being of people living with HIV (PLHIV), and understanding their experiences is essential for optimizing their impact. This review aimed to identify, explore, and synthesize the experiences of PLHIV participating in peer support groups. Methods: A systematic review and meta-synthesis were conducted using the thematic synthesis approach developed by Thomas and Harden. Comprehensive searches were performed in PubMed, Scopus, CINAHL, Cochrane, and Web of Science up to December 2024, using Boolean combinations of keywords related to HIV, peer support, and qualitative research. Studies were included if they used qualitative methods with a focus on PLHIV’s experiences in peer support groups and published in English. Study quality was appraised using the Critical Appraisal Skills Programme (CASP) Qualitative Research Checklist. The review is registered in PROSPERO (CRD42025637718). Results: Out of 1,956 records identified, 20 qualitative studies met the inclusion criteria. The included studies demonstrated substantial geographical diversity, with representation from Africa, North America, Asia, Europe, and Australia. The analysis revealed three main themes: (1) Motivations for Joining Peer Support Groups; (2) Positive Impacts; and (3) Challenges in Participation. Conclusion: Peer support groups help PLHIV gain motivation, emotional strength, and a sense of belonging. Despite these benefits, challenges such as stigma and confidentiality concerns must be addressed through sustainable programs and strong health-community partnerships. © 2026 The Author(s).