ObjectiveTo design, implement and assess an online learning module for third-year and fourth-year medical students addressing medication safety.DesignThis study was a prospective, parallel, open-label, randomised controlled trial with two arms: (1) a control arm in which students were given five articles to read about medication safety, and (2) an intervention arm in which students were given access to an interactive web-based learning module on medication safety. Pretesting and post-testing were done online to evaluate change in medication safety knowledge.ResultsTen students completed the study in the intervention group (online module) and six students completed the study in the control group. The increase in score obtained on the post-test, relative to the pretest, was 15.4% in the group who completed the online module and 2.0% in the control group (difference=13.4%, 95% CI 0.5% to 26.2%, p=0.04).ConclusionStudents who completed an online educational tool about medication safety demonstrated a significantly greater increase in knowledge than those who completed a few readings. Online learning modules can be a convenient and effective means of teaching safe prescribing concepts to medical trainees.