Background: Academic faculty are critical in training future generations of oncologists to care for our increasingly diverse cancer patient population. It is unclear if the growing imperative to address disparities in racial/ethnic and gender representation in the medical field has resulted in corresponding progress in the composition of academic radiation and medical oncology (RO, MO) departments. Herein we report trends in faculty diversity, overall and by academic rank, among US radiation and medical oncologists over the past 5 decades. Methods: Data were acquired from the Association of American Medical Colleges (AAMC) Faculty Roster between 1970-2019 for academic RO and MO departments to determine sex and race/ethnicity trends over five decades. Underrepresented in Medicine (URM) was defined as individuals identifying as Black, Hispanic, and Native American. Linear regression models were used to estimate slopes and associated p-values. Results: Total faculty complements grew over time in both RO and MO departments. The number of URM female faculty increased by 0.85/year in RO and 0.79/year in MO (P-trend<0.001), compared to non-URM female faculty, which increased by 11.3/year in RO and 7.9 in MO (P-trend<0.001). URM male faculty increased by 1.4/year in RO and 1.1/year in MO (P-trend<0.001), compared to non-URM male faculty, which increased by 25.5/year for RO and 12.2/year for MO (P-trend<0.001). Males represented the majority of URM and non-URM faculty for both RO and MO. The proportion of females grew more than the proportion of URM faculty over the study period for both RO and MO. There were also significant differences in diversity by faculty rank. Although MO outperformed RO in terms of the proportion of female faculty members with more advanced rank, female faculty members had a lower academic rank than their male counterparts in both specialties. At every rank, there was a low number of URM faculty represented among both MO and RO (Table). Conclusions: Gender and racial/ethnic diversity of academic RO and MO faculty has increased over time but has not kept pace with the diversity of the US population served, particularly with respect to URM status. The proportion of female faculty in both specialties demonstrates more promising growth, and may inform measures to achieve similar progress in recruiting and retaining URM faculty in both MO and RO.