Background: While it is recognized that SDOH can impact diabetes self-management and glycemic control in underserved YA with T1D, the real-time dynamic interplay among these variables within a given individual is poorly understood, which limits intervention potential. Methods: We recruited 61 underserved YA with T1D (ages 18-30 yo) from the Bronx, New York. We administered 14 days of 3 times daily Ecological Momentary Assessment (EMA) surveys via smartphone, paired with blinded continuous glucose monitoring (CGM). Young adults reported twice daily on their experience of SDOH and once daily on their diabetes self-management. Using dynamic structural equation modeling, we evaluated within-person direct and indirect effects of SDOH on glycemic control, mediated through self-management. Results: We included 51 YA with complete data (mean age 23 yo, 36% Black, 54% Hispanic, 73% Medicaid-insured, mean A1c 8.6%). Within an individual, on days when reported, presence of SDOH predicted lower time in range (TIR, 70-180 mg/dl) by 0.8% and increased mean blood glucose by 1.7 mg/dl that same day, but only when diabetes self-management was affected (indirect pathway). Separately, on days when daily self-management rating was higher, regardless of whether SDOH were experienced, TIR (+6.3%) and mean blood glucose (-14 mg/dl) improved that same day. Conclusions: We examined the daily dynamic interplay of changes in SDOH, self-management, and glycemia in a novel way in underserved YA with T1D. While experiencing daily SDOH negatively affected glycemic control, it was only when self-management was also impacted. Just-in-time self-management support delivered in the context of daily SDOH experiences offers a new approach to timely targeted intervention. Interrupting the chronic cycle of cumulative effects of daily SDOH on glycemia could affect long-term outcomes. Disclosure G.Crespo-ramos: None. C.Schechter: None. M.Finnan: None. C.J.Hoogendoorn: None. J.S.Gonzalez: Consultant; Virta Health Corp. S.Agarwal: Advisory Panel; Medtronic, Consultant; Beta Bionics, Inc., Research Support; Abbott Diabetes, Dexcom, Inc. Funding NY-Regional Center for Diabetes Translational Research (5P30DK111022-08); National Institute for Diabetes and Digestive and Kidney Diseases (K23DK115896-05)