Training of interdisciplinary clinical reasoning and decision-making skills, essential in daily clinical practice in oncological specialties, are still underrepresented in medical education. Therefore, at LMU University Hospital Munich, we implemented a didactically modified tumor board simulation with experts from five different disciplines (medical oncology, pathology, radiation oncology, radiology, and surgery) presenting patient cases into a one-week course on the basic principles of oncology. In this survey, we examined the self-assessed impact of our course on the interdisciplinary decision-making skills of medical students. Between November-December 2023 and January-February 2024, we surveyed two cohorts of medical students in the third year of medical school in our one-week course before and after participating in the tumor board simulation. The objective was to evaluate the self-assessed knowledge in interdisciplinary clinical decision-making, in integrating ethical considerations into clinical reasoning, and in comprehension of various professional viewpoints in interdisciplinary decision-making. Knowledge was assessed using a five-step Likert scale from 1 (no knowledge) to 5 (complete knowledge). The survey was answered by 76 students before and 55 after the simulation, equaling 60-70% of all 100 course participants. Mean knowledge level regarding principles of interdisciplinary clinical decision-making improved significantly in all of the following exemplary aspects: purpose and procedure of tumor boards in clinical practice (from 2.4 ± 1.1 to 4.0 ± 1.0, Spearman's ρ = 0.6, p < 0.001), principles of dealing with ethical challenges in oncology (from 2.4 ± 1.1 to 3.4 ± 1.0, ρ = 0.4, p < 0.001), and principles of shared decision-making in oncology (2.7 ± 1.1 to 3.7 ± 1.0, ρ = 0.4, p < 0.001). Students reported that their skills in clinical decision-making and ability to discuss oncological patient cases from different professional viewpoints improved due to the teaching course. By employing our interdisciplinary one-week course and a didactically modified tumor board simulation featuring experts from various oncological disciplines, medical students' comprehension of interdisciplinary clinical decision-making in oncology improved significantly.