Background: A major contributor to the black-white mortality gap in endometrial cancer (EC) is late stage at diagnosis for black women, which may be driven by delays in diagnosis both prior to and after symptom disclosure. Methods: For phase 1, black women with EC were recruited through oncology clinics and a local cancer support group. In-depth interviews were conducted focused on experiences of menopause, postmenopausal bleeding (PMB), and symptom disclosure, and transcripts coded using directed content analysis. For phase 2, EC cases from 2001–2015 were identified in SEER-Medicare. Location, provider type, and dates of symptom report and diagnosis were defined by claims data. The diagnostic interval was then calculated and step-wise multivariate modeling used to determine factors associated with time to diagnosis. Results: Phase 1 included 11 black women from 4 states (WA, LA, GA, CA), ages 47–70, stages 1––3 at diagnosis, for a total of 147 pages of transcribed interviews. Most were insured, with access to routine medical care. Common themes were a lack of knowledge of normal vs abnormal menopausal symptoms and silencing about bleeding among friends and family. The predominant interpretation of PMB was a resumption of normal menstruation, leading to significant delay in symptom disclosure. Reporting to an MD was largely driven by increased severity of bleeding or the onset of pain. Phase 2 included 3,363 EC cases, with 293 (8%) black women. The median diagnostic interval was 28 days (IQR: 8–110 days). After adjusting for age, region, gynecologic history and other presenting symptoms, provider differences were noted with shorter time for ER MDs (84%; P<.01) and PCPs (16%; P=.05) vs OBGYN. Characterization of bleeding as ‘abnormal’ rather than ‘postmenopausal’ prolonged time to diagnosis by 60% (P<.001). Black race was associated with a 2.4-fold increased diagnostic time interval (P=.017). Step-wise modeling showed that this association was explained by differences in diagnostic work-up: Compared to those with a biopsy within 7 days of presentation, women who had an ultrasound or no procedures had longer intervals (42% and 99%, respectively) to diagnosis (P<.001 for all). Conclusion: Among black women with access to medical care, there are modifiable factors that contribute to delays in diagnosis of EC both prior to and after symptom disclosure to a physician. This is the first study to identify targets for intervention to reduce the mortality rate in this high-risk group.