Background. Background & Purpose: Chronic diseases reduce self-esteem due to prolonged treatment and functional limitations. This systematic review evaluated the effect of peer group support on self-esteem in chronic disease patients and examined its implications for advanced-stage cervical cancer patients undergoing radiotherapy. Methods: Electronic searches across PubMed, Cochrane CENTRAL, and ScienceDirect (2020–2026) yielded 232 records. After removing 23 duplicates, 209 records were screened, 19 full-text reports were assessed, and 9 empirical studies were included in the qualitative synthesis. Methodological quality was evaluated using Joanna Briggs Institute (JBI) Critical Appraisal Tools. Results: Study Characteristics & Quality: Nine studies were included (4 good quality, 5 moderate quality), covering conditions such as post-acute COVID-19 and breast cancer. Zero studies evaluated advanced-stage cervical cancer patients receiving radiotherapy. Impact on Self-Esteem: Heterogeneous and inconsistent across 5 measuring studies—significant improvements occurred in a single-group pre-post study and within-group breast cancer RCT; no significant changes were found in an online pre-post study, an eating-club trial, or in between-group post-intervention comparisons. Related Psychosocial Outcomes: Peer support consistently yielded positive secondary effects, including enhanced self-efficacy, increased social support, better recovery, and reduced illness-related stigma. Conclusion: Peer support interventions offer potential benefits for self-esteem and related psychosocial outcomes in chronic conditions, though direct evidence for self-esteem remains limited and inconsistent. Adequately powered trials using standardized measures are needed.