9004 Background: Many trainees, including Hematology/Oncology (HO) fellows, face burnout throughout their training. Here we implemented a longitudinal curriculum to help fellows with a focus on professional development and burnout mitigation skills. Methods: Interventions to address wellness were initiated in our HO fellowship program in academic year (AY) 2022-2023 based on a needs assessment, including faculty-led sessions, fellow debrief sessions, and social activities (data previously reported). In AY 2023-2024, a new baseline needs assessment was distributed to fellows to determine topics of interest for developing a fellowship retreat and for discussion throughout the year. This assessment also included the Mini ReZ survey to evaluate learning environment, the Patient Health Questionnaire 2 to assess for depressed mood, and the Generalized Self-Efficacy Scale. Surveys were completed anonymously in person and online and were sent throughout the year (data to be fully analyzed by June 2024). T-test and Chi-square test were used for statistical analysis. Results: 22 out of 27 fellows (81.5%) completed the baseline assessment in July 2023. Topics of interest for further discussion included work-life balance, management of scholarly expectations, and professional boundary setting. A day-long, off-site fellowship retreat was designed to address these concerns, with a specific focus on fellow strengths, leadership skills, boundary setting, and communication. Retreats were divided into senior and first-year fellows. Of the 27 fellows who attended the retreats, 22 responded to post-retreat surveys, with 21 of 22 fellows indicating they found the retreat helpful (95.4%). When asked what the most meaningful part of the retreat was, fellows responded “connection with colleagues,” “sharing what inspires/motivates [them],” and “discussing methods to try and prevent burnout.” Scores of self-efficacy and perception of positive learning environment did not significantly differ before and after retreats, and levels of depression remained low. Additional faculty-led didactic sessions were held including a session titled “Grief and Awe” and another titled “Shame Resilience”, with plan for 2 additional sessions. Evaluations of these sessions are planned for the end of the AY to assess effectiveness. Conclusions: The development of a curriculum to address wellness and professional development, including a fellowship retreat that focused on topics identified by a needs assessment, was found to be helpful among HO fellows. More data must be collected to evaluate the effect of these interventions; final data on the entire experience will be available to report at the annual meeting. This curriculum could serve as a model for other programs and be integrated into ASCO’s array of trainee resources to address HO fellow wellness and professional development skills during training.