Background: 25-Hydroxyvitamin D [25(OH)D] levels are lower in obese individuals. Determining whether low vitamin D status can predispose weight gain requires a longitudinal study. Methods: From a community-based multicenter U.S. prospective cohort of 9704 (Study of Osteoporotic Fractures [SOF]), 4659 women aged ≥65 with baseline 25(OH)D measurement were followed for 4.5 years. They were weighed at baseline and follow-up visits, and a subset (n=1054) had 25(OH)D levels remeasured at follow-up. Results: Women with 25(OH)D levels ≥30ng/mL had lower baseline weight (141.6 pounds) compared to women with 25(OH)D levels <30ng/mL (148.6 pounds) (p<0.001). Overall, 25(OH)D status was not associated with weight change over 4.5 years, although there was a significant interaction between 25(OH)D status and weight change category (loss, gain, stable) (p<0.0001). In women who gained ≥5% weight, those with baseline 25(OH)D levels ≥30ng/mL gained 16.4 pounds (12.2% of baseline weight) over 4.5 years compared to 18.5 pounds (13.9% of baseline weight) in women with levels <30ng/mL (p=0.04). In women who lost ≥5% weight or remained stable (<5% weight change), there was no association between 25(OH)D status at baseline and weight change. Among women who gained weight and had 25(OH)D measured at both visits, having sustained or developing 25(OH)D levels ≥30ng/mL was associated with less weight gain between visits (14.81 vs. 16.34 pounds, p=0.04). Conclusions: Higher 25(OH)D levels are associated with lower weight gains, suggesting low vitamin D status may predispose to fat accumulation.