<p>Patients with rheumatoid arthritis have higher rates of mental health problems and lower levels of psychological well-being compared to the general population. This study examines the impact of these factors on the psychological well-being of patients with rheumatoid arthritis. In the trial conducted in 2024, a total of 78 patients were enrolled. They first completed a demographic characteristics form and Ryff’s Psychological Well-being Scale. Subsequently, the patients were randomly assigned to either the intervention group or the control group. The control group received routine care, while the intervention group participated in a peer support group program consisting of 1.5-h weekly sessions over a period of six weeks. These sessions were conducted using the social media platform BALE. The data collection tool was completed by participants immediately after the intervention and again two months after its completion. Data analysis included chi-square, Mann–Whitney, and Friedman tests, as well as Wilcoxon signed-rank tests with Bonferroni correction. A significantly higher score of psychological well-being was observed in the intervention group compared to the control group at the posttest (<i>P</i> &lt; 0.001) and follow-up test (<i>P</i> &lt; 0.03). In terms of aspects of psychological well-being, participants in the intervention group had significantly higher scores on environmental mastery (<i>P</i> = 0.008), positive relations (<i>P</i> = 0.03), self-acceptance (<i>P</i> = 0.007), and personal growth (<i>P</i> = 0.03) compared to patients in the control group at the posttest. Moreover, scores for environmental mastery (<i>P</i> = 0.002) and self-acceptance (<i>P</i> = 0.01) were significantly higher in the intervention group than in the control group at the follow-up assessment. Peer support groups can be a helpful tool for improving the psychological well-being of individuals with rheumatoid arthritis. To further enhance the long-term benefits of these groups, the implementation of a booster program is recommended. Future research could explore and compare the impact of various delivery approaches for peer support groups, such as hybrid models, on the psychological well-being of patients with rheumatoid arthritis.</p><p><i>Trial registration</i> This trial is registered on the Iranian Registry of Clinical Trials website with the identifier IRCT20140519017756N49 (Date: 14/10/2023).</p>