Abstract BACKGROUND: Obesity is a key risk factor for breast cancer (BC) incidence, recurrence, and mortality among post-menopausal African American (AA) women. Many older AA women are likely to report fewer healthy dietary behaviors, and those who are overweight or obese are likely to share similar dietary patterns as their social networks (SNs). AA women are also likely to receive information on BC risk from their SNs. Thus, AA women who share information on healthy dietary behaviors are well-positioned to become change agents toward reducing obesity and improving BC outcomes among their SNs. This presents a novel opportunity to increase the impact of evidence-based (EB) interventions focused on reducing obesity-related BC risk. This study aimed to assess the effects of the MedDiet-SN pilot intervention among participants trained as change agents to improve obesity-related BC risk reduction behaviors for themselves and their SNs through EB information sharing. Methods: MedDiet-SN was a 10-week, pre-/post- pilot intervention promoting the uptake of the Mediterranean diet, with participant training on effective EB information sharing. A community-based participant advisory board informed the pilot. Study procedures were IRB approved. Eligible participants were AA women, ≥60 years old, overweight or obese, Chicago area residents, and with no severe health conditions. Sixteen women participated, and 30 of their SN members (age ≥18 years) were recruited through participant referral. Predictors included time from pre- to post-study and session dosage for participants, and participant EB information sharing on healthy eating for SN members. Outcomes for both groups included BC and diet knowledge, dietary change attitudes (motivation, self-efficacy), dietary behavior change, and BMI. EB information sharing on healthy eating was an additional outcome for participants. Bivariate and multivariate analyses were performed to assess outcomes. Results: In crude and adjusted time models, participants showed improved knowledge, behavior change, BMI, and EB information sharing (p<0.05). In adjusted dosage models, participants showed improved knowledge, attitudes, and EB information sharing (p<0.05). SN members showed improved attitudes and behavior change based on participant EB information sharing on healthy eating (p<0.05). In addition, there was a high concordance between participant EB information sharing and SN EB information learned (>70%). CONCLUSION: This research is innovative in that it 1) shows the effectiveness of a network-based intervention promoting healthy dietary behaviors for obesity-related BC risk reduction among AA women, 2) supports the value of scaling up interventions by leveraging participants as change agents for EB information sharing among SNs, and 3) provides a contribution to emerging research on positive intervention spillover effects to SNs. It is anticipated that results from this study will inform the development of future network-based interventions that aim to reduce obesity-related BC risk and improve health outcomes for AA women. Citation Format: Nyahne Bergeron, Mona Strahan, Patricia Hardmon, Marja Stanford- Leak, Anita Stevens, Annie Young, Devyanne Ward, Lois White, Eunhye Lee, Lisa Tussing-Humphreys, Marian Fitzgibbon, Yamilé Molina. Leveraging African American women as change agents to reduce obesity-related breast cancer risk: An evaluation of a network-based pilot intervention promoting the Mediterranean diet [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr A111.