Abstract Body: Introduction: Postpartum weight retention (PPWR) raises risks for obesity, poor cardiometabolic health, and adverse perinatal outcomes. Lifestyle behaviors promote weight management, yet postpartum intrinsic motivation for them—what people enjoy, value, and do with ease—is poorly understood. Hypothesis: The Pregnancy, Lifestyle and Environment Study-2 (PETALS-2) hypothesized that higher intrinsic motivation for healthy eating, physical activity (PA), and weight self-monitoring predicts less PPWR. Methods: Participants in a large health system were assessed in pregnancy and up to 6 points through ~30 months postpartum (N=311; 22% Asian, 7% Black, 27% Hispanic, 14% multiracial, 30% White; 54% pre-pregnancy BMI ≥25 kg/m²). We prospectively assessed intrinsic motivation via validated surveys on 5-point scales, and weight via electronic health records, remote scales, and study visits. Results: In adjusted linear mixed effects regressions, those with higher intrinsic motivation had less PPWR at 12, 18, 24 and/or 30 months postpartum (Table). For intrinsic motivation for healthy eating, each 1-unit higher score predicted as much as -3.45 lbs. (95%CI: -5.43, -1.47) of PPWR at 24 months; for PA motivation, -2.33 lbs. (-4.14, -0.51) at 30 months; and for self-weighing motivation, -4.4 lbs. (-6.63, -2.22) at 24 months. Magnitude of the latter estimate increased over time. Conclusions: Higher intrinsic motivation for lifestyle behaviors predicted less long-term PPWR in a diverse sample. The magnitude of effects reflects a sizable proportion of the average PPWR shown in long-term studies, suggesting clinically meaningful impact. Novel interventions could target intrinsic motivation to improve PPWR and maternal cardiometabolic health.