People living with HIV (PLWH) continue to face psychological burdens linked to stigma, disrupted identity, and emotional isolation. Peer-led support groups have emerged as community-based strategies to address these challenges, yet their mental health benefits remain under-explored within psychological research. This study offers a cross-cultural qualitative comparison of how peer support groups function as informal therapeutic spaces for PLWH in Indonesia and Denmark, highlighting shared psychological benefits and culturally distinct coping strategies. The study aimed to explore how peer-led support groups reduce HIV-related stigma and enhance psychological quality of life in two culturally different contexts. Framed within health psychology and social development perspectives, it examined how peer networks facilitate emotional support, self-advocacy, and cultural adaptation of HIV care beyond clinical settings. We conducted 40 in-depth, semi-structured interviews with PLWH (20 in each country) who had participated in peer support groups for at least six months. Participants were purposively selected to reflect diversity in gender, age, and treatment experience. Thematic analysis was applied using a psychological lens, focusing on emotional expression, meaning-making, and interpersonal processes. Three core psychological functions of peer support groups were identified: emotional relief and regulation, identity reconstruction, and empowerment. Participants described groups as safe spaces to express emotions, reframe their HIV identity from shame to resilience, and build confidence in managing care. Cultural differences shaped these processes: Indonesian participants emphasized collective identity and spirituality, while Danish participants highlighted autonomy and self-affirmation. Across both settings, peer support enhanced motivation, psychological clarity, and sustained care engagement. Peer-led support groups offer low-cost, culturally adaptable, and psychologically meaningful interventions. Their integration into HIV care systems may help close mental health gaps, reduce stigma, and improve quality of life for PLWH globally.