Background <p>Multiple sclerosis (MS) is a chronic autoimmune disease affecting the central nervous system. Conventional treatments often fail to adequately address symptoms such as sleep disturbances.</p> Objective <p>To investigate the efficacy of music therapy as a complementary intervention in improving sleep quality among patients with relapsing-remitting multiple sclerosis (RRMS).</p> Methods <p>This randomized controlled trial enrolled 60 RRMS patients from the Comprehensive MS Center in Mashhad between June and September 2024. Sample size was calculated based on a medium effect size (Cohen’s d = 0.5), yielding 54 participants, which was increased to 60 to account for potential attrition. Participants were randomly assigned to an intervention group (music therapy plus standard care) or a control group (standard care only). The intervention consisted of music therapy sessions three times daily for two weeks. Sleep quality was assessed at baseline and post-intervention using the Pittsburgh Sleep Quality Index (PSQI), including its seven subscales. Data were analyzed with SPSS version 26.</p> Results <p>Baseline PSQI scores were similar between groups (10.5 ± 2.8 vs. 11.8 ± 3.3, <i>p</i> = 0.093). Post-intervention, the intervention group showed a statistically significant improvement compared to the control group (9.4 ± 2.6 vs. 10.9 ± 3.0, <i>p</i> = 0.047). While within-group changes were not significant, improvements were most notable in subjective sleep quality, sleep latency, and daytime dysfunction, reflecting modest clinical effects.</p> Conclusion <p>Music therapy is a safe, accessible, and cost-effective complementary intervention that improves sleep quality in patients with RRMS. Reliance on subjective measures is a limitation; future studies should include objective sleep assessments.</p> <p><i>Trial registration</i> IRCT20231001059576N1, registered November 04, 2023.</p>