This study investigated the effectiveness of three different versions of a training programme on physician-patient and teacher-parent conversations for medical students and student teachers. The research questions concerned the differential effects of e-learning featuring contrastive video cases, role-play including video feedback and their combination. The training effects were tested to determine whether they were similar across both professional domains. In a randomised controlled trial (N = 168), three training conditions were prepared using a wait-list control group. The assessment of communication competence was based on videotaped communications between the participants and simulated patients/parents (i.e., trained actors). The results of planned contrast analyses corroborated the study expectations: first, a strong overall treatment effect was observed. Second, the combined condition was more effective than e-learning and role-play alone when controlling for prior knowledge and cognitive ability. Third, e-learning proved more effective than role-play. Exploring interaction effects indicated that student teachers benefited more from the training than medical students.