Treating patients with breast cancer is multidisciplinary; however, it is unclear whether surgery residency programs provide sufficient training in multidisciplinary care. Self-efficacy is one way of measuring the adequacy of training. Our goal was to develop a method of assessing self-efficacy in multidisciplinary breast cancer care. Based on a literature review and subject-matter expert input, we developed a 30-item self-efficacy survey to measure six domains of breast cancer care (genetics, surgery, medical oncology, radiation oncology, pathology, and radiology). We constructed and validated the survey using a seven-step survey development framework. The survey was administered to general surgery residents at a single academic surgical residency. Response rate was 66% (n = 31). Internal consistency was strong (Cronbach alpha = 0.92). Self-efficacy was moderate (mean = 3.05) and tended to increase with training (postgraduate year [PGY] 1: mean= 2.37 versus PGY 5: mean= 3.54; P < 0.001), providing evidence for construct validity. Self-efficacy was highest in the surgery (3.56) compared with others (genetics 2.67, medical oncology 3, radiation oncology 2.67, pathology 2.67, and radiology 3.33). This trend was similar across all PGY groups, except for interns, whose self-efficacy in surgery was low. We created a survey to assess self-efficacy in multidisciplinary breast cancer care and provided initial evidence of survey validity. Although self-efficacy in surgery improved with years in training, medical and radiation oncology self-efficacy remained low. As modern breast cancer treatment is highly multidisciplinary, an expanded education program is needed to help trainees incorporate multidisciplinary clinical perspectives. • Self-efficacy is one's belief in ability to learn new knowledge or skills. • Surgery resident self-efficacy in breast surgery increases with years in training. • Resident self-efficacy in multidisciplinary care of breast cancer remains low. • Novel educational module needed to address multidisciplinary care in breast cancer. [ABSTRACT FROM AUTHOR]