Abstract Background: Breast cancer is the most commonly diagnosed cancer among Korean American women and incidence in this group is rising. Advanced-stage disease is more frequent among Korean women diagnosed with breast cancer than in other ethnicities due to low adherence to screening. Lower socioeconomic status, cultural barriers, perceived norm, distrust of healthcare system, and lack of awareness and culturally tailored communication on benefits of screening contribute to low screening utilization. Church settings offer important platforms for education as a majority of Korean American women >50 years regularly attend church services. Thus, the objective of this trial was to evaluate the efficacy of a culturally tailored intervention “Faith in Action!” on breast cancer screening adherence rates among Korean American women. Methods: A parallel cluster randomized trial with staggered roll-out will be conducted to evaluate the efficacy of the “Faith in Action!” intervention, a church-based small group education and lay health navigator program, delivered by trained church members, on breast cancer screening among Korean American women (NCT05298605). This study was designed and conducted in partnership with a Community Advisory Board. Trial enrollment began in July 2022 and is ongoing. Twenty-four total Korean churches in Los Angeles were randomized within blocks of 8 churches to either intervention or waitlist control conditions in a 1:1 ratio. Using a train-the-trainer approach, lay navigators from the Korean Church community nominated by church leadership are trained and certified to deliver the Faith in Action! intervention to study participants over a 6-month program period. Participants at churches randomized to the waitlist control group receive an educational presentation on physical activity and nutrition and, after 6-month follow-up, are invited to receive the Faith in Action! intervention. Eligible participants include women of Korean descent, ages 45-75 years, who: attend a participating church, do not have a breast cancer diagnosis, and did not receive mammogram in the last 2 years. The primary outcome is adherence to breast cancer screening guidelines within 6 months from end of program. Secondary outcomes include adherence to breast cancer screening within 1 year and participant knowledge about breast cancer screening practices. Qualitative interviews will be conducted to assess participants’ knowledge and barriers surrounding cancer screening decisions and program acceptability. To date, 16 churches (149 total participants) have been enrolled in the study and are being followed. It is expected that findings from this research will inform community-based efforts to increase breast cancer screening adherence among Korean American women and improve understanding of screening barriers in this group that is disproportionately impacted by breast cancer, while building capacity and opportunities for sustainability in the Korean faith community. Citation Format: Gillian Gresham, Christie Y. Jeon, Dong Hee Kim, Min Jung Sung, Laurel J. Finster, Marcio A. Diniz, Michael Fine, Zul Surani, Alison K. Herrmann, Jeong Yup Lee, Robert W. Haile. A cluster randomized trial to evaluate a church-based navigation model to increase breast cancer screening in Korean women (Faith In Action!): Trial in progress [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT272.