This study describes the experience of a postgraduate clinical psychology student working with children with cancer and their families as part of a training program that incorporated entrustable professional activities (EPAs) into its framework. The student was supervised by a clinical supervisor. The training program involved providing psychological care for 16 children with cancer in the pediatric ward of a medical center from August to November 2020. The student and supervisor both assessed EPAs corresponding to the six general competencies defined by the Accreditation Council for Graduate Medical Education and used quantitative and qualitative two-way feedback to explore the relationship between EPAs and the core competencies. The quantitative results revealed progressive improvement over the different training phases, and qualitative feedback indicated increased comprehension by and self-modification from the student. This information can be used to assess the student’s performance and authorization for managing EPAs. Programs that adopt EPAs would benefit from increased participation by clinical supervisors, who are best positioned to discuss, revise, and support the implementation of EPAs to ensure their reliability and validity, thereby optimizing educational effectiveness and the quality of health-care services.