Abstract Background/Introduction: The purpose of this study is to examine the feasibility of engaging African American (AA) men as Citizen Scientists (CSs) to support the engagement, recruitment, and retention of AA men in a prostate cancer (PCa) study to validate a new biomarker, Prostate Health Index (PHI) in AA men. AA men are traditionally under-represented in PCa research. Additionally, PCa screening studies that have sought to validate innovative ways of improving the screening of PCa often exclude or do not intentionally focus on the engagement of AA men. Using a Community Engaged Participatory Research (CBPR) model, this study purposes to engage the social networks of AA men trained as CSs to engage and recruit a cohort of healthy controls as a low-cost first step in validating PHI as a PCa screening test in AA men. Methods: Building upon the social networks of the multi-PI team from 3 academic medical institutions and 2 community-based organizations, we sought to identify, recruit, and train 8-12 AA men as CSs. A CS training curriculum was developed and adapted from other CS training models to meet the specific needs of AA men engaged in PCa research. A training series of 5 two-hour modules was developed for the CSs; module 5 is a booster. Validated surveys and post-training evaluations were administered to CSs to assess medical mistrust, cancer knowledge, and adverse childhood experiences. Post-training questionnaires were used to assess quality of training and areas for improvement. Sessions were conducted using CBPR principles to allow CSs to inform the recruitment and retention approaches for AA men in the CSs social network. CSs and PIs collaboratively developed a series of recruitment events within their social networks. IRB approval was obtained across the three academic partners involved. Results: Nine AA men from the social networks of the multi-PI team have been identified. The 9 CSs include 3 PCa survivors, 2 faith-based leaders, 1 fraternity order member, 1 civic leader, 1 barber, and 1 community social worker. The CSs have completed 3 of 5 modules. All the 9 CSs have completed CITI IRB training and are key personnel in the research protocol. Attendance at meetings ranged from 75-100%. Medical mistrust was high among AA CSs. All CSs strongly agreed that their contribution to AA health equity was a reason for their participation. To date, one pilot community event has been developed from the social network of the faith-based and civic CSs. Six events have been planned for summer/fall 2018 to reach Year 1 recruitment goals. Conclusion: Early outcomes indicate that it is feasible to engage/train AA men as CSs to conduct PCa disparities research. Attendance and survey data suggest that AA male CSs are willing to support AA-focused PCa disparities research. Pending the assessment of the recruitment feasibility of AA men, this represents a potentially scalable model for engaging AA men in cancer disparities research and for leveraging social networks to support recruitment and retention of AA men in cancer disparities research. Citation Format: Karriem S. Watson, Josef Ben Levi, Tiffany McDowell, Alfreda Beth-Holloway, LeAndre Moore, Ivanhoe Hall, Alexander Kimbrough, Pooja Gogana, Robert A. Winn, Marcus Murray, Adam Murphy. Engaging African American men as citizen scientist to validate a prostate cancer biomarker [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr A036.