BACKGROUND Medication nonadherence is an important barrier to achieving optimal clinical outcomes. Currently, there are limited data on methods used to train medical students about medication adherence. OBJECTIVE To evaluate the knowledge, confidence, and attitudes of first-year osteopathic medical students before and after a 30-minute peer-to-peer medication adherence education program led by a third-year pharmacy student. METHODS All first-year medical students from Touro University California College of Osteopathic Medicine were invited to participate in 1 of 3 medication adherence educational sessions held in May 2019. A third-year pharmacy student who received training from Touro University California College of Pharmacy faculty served as the peer educator. Each session took approximately 1 hour to complete. The session included a preprogram survey, a 30-minute program, and a postprogram survey. Survey items included demographics; medication adherence knowledge, confidence, and attitudes; and attitudes toward the peer-to-peer educational format. Statistical comparisons of preprogram and postprogram knowledge, confidence, and attitudes were made using a paired t test, the McNemar test, and the Wilcoxon signed-rank test. P<.05 was considered statistically significant. A sample size calculation was performed using mean knowledge scores to determine whether the study achieved 80% power. RESULTS Twenty-three students participated in the study. Medication adherence knowledge scores improved after the program (17.4 [77.4%] vs 9.98 [92.2%]; P<.001). Confidence scores also improved for all 7 survey items (P<.001). Medical students had more positive attitudes toward medication adherence after the program, with 8 of 10 survey items in this domain showing improvement. Most students had a positive attitude toward the peer-to-peer educational format. All participants reported that they would implement the medication adherence skills learned at the program with future patients. CONCLUSIONS A 30-minute peer-to-peer program led by a pharmacy student improved first-year medical students' knowledge, confidence, and attitudes with regard to medication adherence and provided an effective format to enhance interprofessional learning and collaboration.