Abstract Background: The side-effects of adjuvant endocrine therapy treatment (AET) are one of the main reasons why women discontinue therapy. Helping women manage the side-effects may improve adherence since only half are adherent for 5-years. Generally, patients experience a decline in social support from family/friends and medical providers when beginning AET because the severity of the side effects are not as physically apparent as those associated with other cancer treatments. Therefore, the objective of this study is to explore the role of social support and identify how it is delivered during the on-going management of AET. Methods: We conducted semi-structured in-depth interviews with breast cancer patients (n=19) who had filled a prescription for AET in the previous 12 months. Women were recruited from Los Angeles, California and Houston, Texas between 2014-2015. Interviews were audio recorded and professionally transcribed. Interview questions were designed to prompt discussion about experiences with AET and examine how sources of support affect the management of AET drugs. We used an integrated approach to develop a code structure, which was applied to interview transcripts using qualitative inductive reasoning to identify major themes and subthemes. The study team met regularly, in an iterative process, to redefine the codebook by adding, removing, and revising codes to capture emerging themes. We grouped social support into four major categories to identify the sources and delivery of support: emotional, informational, instrumental, and appraisal. Results: Patients most commonly described informational support from their medical providers via consultations or phone, during which providers would explain the purpose, benefits, and side-effects of AET in a manner that they could understand. Many patients confided in their health providers when struggling with the side-effects of AET, and those who were well-received expressed trust and confidence in their physician's recommendations. Women also discussed other noteworthy sources of informational support through technology, survivorship groups, family/friends, and religious groups. Emotional support was an equally important type of social support as patients discussed the need for ongoing reassurance, communication, and empathy to help them deal with the stressors of managing their side effects, which they received from family, survivorship groups, and different forms of spirituality and religiosity but could also be delivered by medical providers. Instrumental and appraisal support played a more peripheral role as patients identified different types of organizations and exercise classes that provided them with physical and emotional benefits and that was provided by family/friends and medical providers. Conclusion: We identified all four forms of social support delivered to a group of breast cancer survivors on active AET in formal and informal settings by family/friends, medical providers, and support groups. The social support provided women with educational, physical, and emotional benefits that may play an important role in their continuation of AET. Citation Format: Toledo G, Ochoa CY, Farias AJ. Exploring the role of social support and adjuvant endocrine therapy use among breast cancer survivors [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-13-16.