BackgroundBoth adolescent and young adult (AYA) and Black or African American (hereafter referred to as Black) cancer patients are historically under‐enrolled in cancer treatment trials (CTT). The purpose of this study was to quantify enrollment of Black AYAs in National Cancer Institute (NCI)‐sponsored CTTs overall and by age, sex, and cancer diagnosis during 2000–2015.MethodsUtilizing data from NCI’s Cancer Therapy Evaluation Program and the Surveillance, Epidemiology and End Results (SEER) Program, we assessed CTT enrollment in Black patients with cancer and measured changes in enrollment over time between the study periods 2000–2007 and 2008–2015. Enrollment patterns were compared across age groups (≤14 years [y], 15–19y, 20–29y, 30–39y and 40+ years), sex, and cancer diagnosis.ResultsFrom 2000 through 2015, <3% of Black AYAs (20–39y) enrolled on CTTs. While AYAs had significantly higher cancer incidence than children, 20.5% fewer Black AYAs enrolled on CTTs. Enrollment was lowest among Black males 20–29y, with a mean of 18 enrolling in CTTs annually. The proportion of AYA enrollees who were Black did not change significantly over time periods (2000–2007 vs 2008–2015).ConclusionsFew Black AYAs enroll in CTTs each year. Given known benefits of clinical trial participation and the well‐documented racial and age‐related differences in cancer outcomes, addressing barriers to enrollment in these patients may, in turn, reduce disparities. Targeted interventions aimed at increasing the CTT enrollment of Black cancer patients, particularly young Black men, are urgently needed.PrecisThis study documents that compared with Black children, Black adolescent, and young adult (AYA) patients were less likely to enroll in NCI‐sponsored CTTs from 2000 to 2015. Black AYA male enrollment decreased with increasing age, highlighting disparities among this specific population in CTT enrollment.