Key PointsQuestionWhat factors are associated with patient-reported unmet supportive care needs in ambulatory oncology, and are these unmet needs associated with the risk of emergency department visits and hospitalizations?FindingsIn this cohort study of 5236 ambulatory patients with cancer, Black race, Hispanic ethnicity, greater number of years after diagnosis, depression, poor physical function, and low health-related quality of life scores were associated with greater unmet needs. Compared with patients without unmet needs, those who reported having unmet needs had a significantly higher risk of emergency department visits and hospitalizations.MeaningThese findings suggest that unmet supportive care needs are associated with clinical outcomes, particularly in racial and ethnic minority populations; addressing these unmet needs is imperative for improving clinical outcomes, and efforts should target specific populations.