Organ transplantation saves lives and improves the quality of life of patients who would otherwise depend on costly and invasive treatments. The technology is becoming available in low- and middle-income countries, but the gap between the demand for and the supply of organ transplants remains large. In a randomized controlled trial at a Tunisian university, we evaluate an expert-led intervention designed to inform about organ donation and strengthen trust in medical institutions. We find that the intervention significantly increases deceased organ donor registration among treated students. There is evidence for positive spillover effects on the control group. The survey data provides little support for changes in attitudes and social expectations as potential mechanisms. Instead, it reveals large and statistically significant increases in medical and legal knowledge, religious beliefs supportive of donation, and institutional trust among treated students. Finally, we show that family attitudes strongly predict the actual decision to register as a donor. Targeting older segments of the population may further increase the impact and cost-effectiveness of this intervention.