OBJECTIVES: This study aimed to explore factors influencing satisfaction with medical services among medically underserved populations at the free medical clinic, providing data to improve free medical services for these populations. METHODS: We employed a descriptive correlational study design involving 112 individuals (aged 19 years and older) from medically underserved populations who visited the clinic. Data were collected through face-to-face surveys from September to October 2023, and statistical analyses (t-tests, analysis of variance, Pearson correlation, and hierarchical multiple regression) were used to identify key predictors of satisfaction. RESULTS: Perceived support from healthcare providers emerged as the strongest predictor of satisfaction with medical services, demonstrating a significant positive association. While social support was positively correlated with perceived support from healthcare providers, it did not independently predict satisfaction. CONCLUSION: These findings underscore the importance of healthcare provider and social support in increasing satisfaction with medical services among medically underserved populations. Developing tailored healthcare programs and specialized healthcare provider training are essential strategies to improve healthcare access and outcomes for these vulnerable groups.