There has been conflicting evidence regarding the potential role of vitamin D in glucose homeostasis. This double-blind randomized placebo-controlled trial was designed to investigate the effect of vitamin D3 supplementation on the disposition index in non-diabetic Indian subjects with obesity. Subjects with obesity [n = 120] were randomized to receive a monthly dose of 120,000 IU of vitamin D3 or matching placebo for 6 months. The primary outcome was a change in disposition index (DI) and secondary outcome measures were change in the homeostatic model assessment of insulin resistance and change in body composition. A total of 101 subjects [50 in the vitamin D group (VITD) and 51 in the Placebo group (PL)] completed the study. The mean baseline serum 25-hydroxyvitamin [25(OH) D] concentration was 11.6 ng/ml. There was no significant difference observed between the two groups in any of the primary or secondary outcomes. However, there were a significant increase in median serum 25(OH) D levels in the VITD group than the PL at 6 months of intervention. The results of the present study suggest that supplementation of vitamin D3 has no additional benefit over placebo on pancreatic β-cell functions in non-diabetic Indian subjects with obesity. Further larger studies are required to confirm the results of the study. The trial is registered with the Clinical Trials Registry of India, CTRI/2015/04/005727.