Objective: Suicide has become a great concern worldwide. A majority of people who completed suicide visited physicians before their deaths, so that physicians are important gatekeepers for suicide prevention. The aim of the present study was to assess the effectiveness of a three-hour suicide prevention program (SPP) embedded in the community medicine course for post-graduate year (PGY) residents over an eight-year period. Methods: The convenient sample was recruited from those who attended the PGY community small-group tutorial program. Each group consisted of 10-20 trainees who completed a post-course survey for course effectiveness evaluation. The survey had three parts: 1) Five-question Teaching Effectiveness Assessment Scale (TEAS) measuring goal expected, teaching format, teaching skill, course benefit, and overall satisfaction; 2) a ten-question written test on suicide-related literacy; and 3) two questions regarding willingness to promote a suicide risk screening tool (The Five-item Brief Symptom Rating Scale, BSRS-5) and to perform suicide gatekeeper skills in practice. Results: A total of 1519 participants joining the program from 2009 to 2016 were analyzed. Results indicated that the ratings for program effectiveness were highly satisfactory on all five dimensions and showed significant improvement across the eight-year period; however, the results of the written test were less satisfactory with a rate of accurate response between 70-80%. A great majority of participants expressed their willingness to promote the BSRS-5 (99.0%) and gatekeeper skills (99.6%) in future practice. Stepwise multiple regression analysis revealed that both course benefit and expected goal significantly predicted willingness to promote the BSRS-5 and to apply gatekeeper skills. Conclusions: Based on the eight-year observation results, the brief suicide prevention program demonstrated its ongoing effectiveness in teaching outcomes and trainees' positive attitudes about being a suicide gatekeeper. The study implied that the brief SPP is applicable for PGY residents.