What does oncologists' grief over patient loss look and feel like? What is the impact of this grief on oncologists' personal and professional lives? This qualitative study explores these questions in depth. Oncologists' grief was found to be a unique, affective mourning experience that included a sense of self-doubt, guilt, failure, holding hard knowledge, powerlessness, sadness, loss of sleep, and crying. The impact of patient loss on oncologists included burnout, compartmentalization, and a normalization of death. Emotional impact on oncologists included difficulty keeping emotional boundaries and emotional exhaustion. Impact on patients included treatment decisions, distraction, distancing and withdrawing from dying patients, and being motivated to improve care for patients. Personal impact included grief spillover and gaining perspective on life. Patient loss has a significant impact on oncologists' personal and professional lives. Education and institutional support are necessary to help oncologists cope better with loss and grief and may have a positive impact on patient care.