Discussing end-of-life decisions with cancer patients is a crucial skill for physicians. This article reports findings from a pilot study evaluating the effectiveness of a computer-based decision aid for teaching medical students about advance care planning. Second-year medical students at a single medical school were randomized to use a standard advance directive or a computer-based decision aid to help patients with advance care planning. Students' knowledge, skills, and satisfaction were measured by self-report; their performance was rated by patients. 121/133 (91%) of students participated. The Decision-Aid Group (n = 60) outperformed the Standard Group (n = 61) in terms of students' knowledge (p < 0.01), confidence in helping patients with advance care planning (p < 0.01), knowledge of what matters to patients (p = 0.05), and satisfaction with their learning experience (p < 0.01). Likewise, patients in the Decision Aid Group were more satisfied with the advance care planning method (p < 0.01) and with several aspects of student performance. Use of a computer-based decision aid may be an effective way to teach medical students how to discuss advance care planning with cancer patients.