PURPOSE: We aimed to understand how new diagnosis discussions are conducted in pediatric oncology, and the training provided for their conduct. METHODS: This mixed-methods study used a sequential exploratory design. Qualitative interviews (n = 20) were conducted with pediatric oncologists (n = 15) and fellows (n = 5) at a single institution, focusing on the process used to convey the diagnosis and treatment plan to the family. Accreditation Council for Graduate Medical Education–accredited pediatric oncology fellowship program directors (n = 38) and fellows (n = 70) were subsequently surveyed to confirm qualitative results and elucidate the training that fellows receive in conducting new diagnosis discussions. RESULTS: Our findings suggest that new diagnosis discussions in pediatric oncology are typically conducted in three stages: (1) concern for cancer; (2) confirmation of diagnosis; and (3) treatment plan/consent, and are fundamentally similar across settings; however, pediatric oncologists skillfully tailor their approach on the basis of clinical circumstances and parental needs. Decisions regarding inclusion of the child are primarily determined by parental preference, whereas inclusion of health care team members is driven by physician role (ie, trainee v program director) and health care organization–related factors. Physician preparation for discussions involves logistical, intellectual, and emotional components. Disclosure of prognosis is nuanced. There is variability across pediatric oncology fellowship programs in the provision of training for these discussions. CONCLUSION: We identified common practices of pediatric oncologists as they prepare for and lead new diagnosis discussions in pediatric oncology. We found variability in the training that pediatric oncology fellows receive regarding how to conduct these discussions, highlighting a need for standardized training curricula.