Case-based learning (CBL) is a learner-centric educational approach that fosters independent learning and exploration through case analysis, guided by teachers' heuristic instruction. The study aimed to evaluate the efficacy of CBL versus traditional teaching methods in advanced breast cancer education for residents. In this randomized controlled trial, 40 residents undergoing standardized training in the Department of Breast Oncology at Peking University Cancer Hospital were enrolled and were equally divided into CBL and traditional teaching groups. Their performance, self-assessment, and course satisfaction were evaluated through post-study examinations and questionnaires. Results showed that the CBL group achieved significantly higher overall scores than the traditional teaching group (88.10 ± 3.72 vs. 85.52 ± 3.27, p = 0.025), with a notable advantage in clinical practice scores (44.54 ± 2.25 vs. 41.83 ± 2.26, p < 0.001). However, theoretical knowledge scores did not differ significantly. Furthermore, the CBL group outperformed in clinical reasoning (p = 0.018), self-learning capabilities (p = 0.037), and problem-solving skills (p = 0.037). Satisfaction levels were higher in the CBL group (95%) compared to the traditional group (85%) without statistically significant difference. This study demonstrates the superiority of the CBL method in enhancing the education of residents in advanced breast cancer relative to traditional teaching approaches, supporting the broader application of CBL in medical oncology education.