Vitamin D deficiency is common among South Asians with prevalence rates ranging from 30% to 90%. It is especially prevalent among obese individuals. Vitamin D deficiency causes osteoporosis leading to fragility fractures. It is also implicated in development of cardiovascular disease and cancer. In this study we aimed to assess the prevalence of vitamin D deficiency and insufficiency among Sri Lankan obese patients undergoing bariatric surgery. We did a retrospective analysis of medical records of 80 obese patients who underwent bariatric surgery at Colombo South Teaching Hospital, Sri Lanka. Overall 85.0% were females. Vitamin D deficiency was defined as 25-hydroxyvitamin D level less than 20 ng/ml. Vitamin D insufficiency was defined as 25-hydroxyvitamin D level between 20 ng/ml and 30 ng/ml. Vitamin D sufficiency was defined as 25-hydroxyvitamin D level more than 30 ng/ml. The mean age was 39.1 (±10.6) years. Mean body weight and body mass index were 114.6 (± 23.4) kg, and 45.9 (± 7.3) kg/m2 respectively. Mean 25 hydroxyvitamin D level was 17.0 (±7.5) ng/ml. Overall 72.5% of patients were vitamin D deficient (< 20ng/ml) while 23.8% were vitamin D insufficient (20-30 ng/ml). Only 3.7% of patients were vitamin D sufficient. There was no significant difference in vitamin D levels among males and females (18.0 vs 16.8 ng/ml, p =0.62). Age of patient, body weight or BMI were not associated with vitamin D levels. In conclusion, vitamin D deficiency is extremely common among obese Sri Lankan patients undergoing bariatric surgery with 96.3% of individuals being either vitamin D deficient or insufficient. Thus it is essential to check vitamin D levels in patients undergoing bariatric surgery and to correct the deficiency preoperatively. In addition, obese Sri Lankans should be considered for routine screening for vitamin D deficiency due to the very high prevalence rate in this population.