(1) The aim of our study was to determine the attitudes of medical students toward organ donation in the case of brain death. (2) The study was conducted among 1348 medical students from three medical universities in Poland. The research tool was the Polish version of the standardized questionnaire concerning attitudes toward organ donation and transplantation (ODT) [PCID-DTO RIOS: A questionnaire designed by the 'International Collaborative Organ Donation project about organ transplantation and donation]. (3) Some sources of information on organ donation were found to have a significant impact on the recipients' knowledge of brain death. These were books, friends, family, lectures in other centers, social media, and the Church. Medical students holding the opinion that recovery and leading a normal lifestyle after brain death is impossible were significantly more likely to donate their organs after death, not for religious reasons and not because they wanted to survive their own death. (4) The medical students in our study showed a high level of awareness and favorable attitudes toward ODT. However, the number of registered donors was low. It is important to educate students on these issues to raise the awareness of both future medical professionals and the public on organ transplantation procedures. The public should be made aware that transplantation procedures are of a high standard, and that the law protects both donors and recipients. These measures would reduce recipients' waiting time, and certainly increase the statistics of the number of life-saving and health-saving procedures.