Objectives: To assess the association between obesity (measured by Body Mass Index (BMI) and fat percentage) and serum 25(OH)D levels in older persons. Design: Cross-sectional analysis of data from ‘the B-PROOF study’ (B-vitamins for the Prevention Of Osteoporotic Fractures). Participants: 2842 participants aged 65 years and older. Measurements: BMI and fat percentage, measured by Dual Energy X-ray, and serum 25(OH) D levels. Results: Mean age was 74 years (6.5 SD), with 50% women. Mean serum 25(OH)D levels were 55.8 nmol/L (25 SD). BMI and total body fat percentage were significant inversely associated with serum 25(OH)D levels after adjustment for confouders (β−0.93; 95%CI [−1.15; −0.71],