BackgroundSocial determinants of health (SDH) are intricately intertwined with various social and economic factors. Reflection is essential for learning about SDH. However, only a few reports have focused on reflection in SDH programs; most were cross-sectional studies. We aimed to longitudinally evaluate a SDH program in a community-based medical education (CBME) curriculum that we introduced in 2018 based on the level of reflection and content on SDH in students’ reports.MethodsStudy design: General inductive approach for qualitative data analysis. Education program: A 4-week mandatory clinical clerkship in general medicine and primary care at the University of Tsukuba School of Medicine in Japan was provided to all fifth- and sixth-year medical students. Students underwent a 3-week rotation in community clinics and hospitals in suburban and rural areas of Ibaraki Prefecture. After a lecture on SDH on the first day, students were instructed to prepare a structural case description based on encounters during the curriculum. On the final day, students shared their experiences in a small group session and submitted a report on SDH. The program was continuously improved and faculty development was provided. Study participants: Students who completed the program during October 2018–June 2021. Analysis: Levels of reflection were categorized as reflective, analytical, or descriptive. The content was analyzed based on the Solid Facts framework.ResultsWe analyzed 118 reports from 2018–19, 101 reports from 2019–20, and 142 reports from 2020–21. There were 2 (1.7%), 6 (5.9%), and 7 (4.8%) reflective reports; 9 (7.6%), 24 (23.8%), and 52 (35.9%) analytical reports; and 36 (30.5%), 48 (47.5%), and 79 (54.5%) descriptive reports, respectively. The others were not evaluable. The number of Solid Facts framework items in reports were 2.0 ± 1.2, 2.6 ± 1.3, and 3.3 ± 1.4, respectively.ConclusionsStudents’ understanding of SDH deepened as the SDH program in the CBME curriculum improved. Faculty development might have contributed to the results. Reflective understanding of SDH might require more faculty development and integrated education of social science and medicine.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12909-023-04320-2.