100 Background: Accrual of Black participants to cancer clinical trials remains a major challenge across the country. Here, we report the outcomes of a five-year initiative of community outreach and engagement to improve enrollment of adult Black participants to clinical trials at the Abramson Cancer Center (ACC) at the University of Pennsylvania. Methods: Primary metrics were the percentage of Black patients among all cancer cases in our catchment area, the percentage of adult Black patients cared for at the ACC, and the percentage of adult Black participants enrolled on the three types of NCI-defined clinical trials. Results: In 2014, at baseline, Black residents comprised 19% of the population and 16.5% of cancer cases in our catchment area surrounding Philadelphia, but only 11.1% of ACC patients were Black. The percentages of Black participants accrued onto treatment, non-therapeutic interventional, and non-interventional trials were 12.2%, 8.3%, and 13.0%, respectively. We then established a center-wide program with community guidance to address these gaps. Key elements of the program included: 1) culturally tailored marketing strategies for cancer clinical trials; 2) plans for each protocol to facilitate Black participant enrollment; 3) new partnerships with faith-based organizations serving Black communities to conduct educational events about clinical trials; 4) pilot programs with Lyft and Ride Health to address transportation barriers; 5) patient education by nurse navigators regarding cancer and clinical trials; and 6) an improved informed consent process. These efforts reached more than 10,000 individuals in venues including churches, neighborhoods, community parks and centers, and health centers with formats ranging from educational forums to wellness fairs. Reassessing metrics in 2018, we found that the percentage of Black patients seen at ACC had increased to 16.2%, matching the percentage of Black cancer patients among all cancer cases in our catchment area (16.5%). Total cancer clinical trial accrual had increased from 9,308 participants in 2014 to 13,170 in 2018 (41.5% increase). The percentages of Black participants accrued onto treatment, non-therapeutic interventional, and non-interventional trials were 23.9%, 33.1%, and 22.5%, respectively – a 1.7- to 4.0-fold increase in five years and higher than the percentage of Black patients seen at the ACC. Conclusions: Our multifaceted, community-based engagement initiative to encourage clinical trial enrollment was associated with improved accrual of Black participants to cancer clinical trials. These findings also suggest that gaps in access to cancer centers are a key factor driving access to clinical trials. Medicaid expansion occurred concurrently in all states in our catchment area and its impact on accrual merits further research.