BACKGROUND: Vitamin D has a significant role to play in bone metabolism and neuromuscular function. Several researchers have indicated that Vitamin D deficiency may be possibly related to chronic musculoskeletal pain including chronic low back pain (CLBP). OBJECTIVES: The present study was conducted to determine the prevalence of hypovitaminosis D and its contribution to chronic lower back pain. STUDY DESIGN: Controlled study. SETTING: Outpatient pain clinic of tertiary care hospital. METHODS: Data presented in this manuscript are from patients who were screened for inclusion in an open label, single arm clinical trial aimed to assess the effectiveness of vitamin D supplementation in patients with CLBP. Consecutive patients visiting the outpatient pain clinic of a tertiary care hospital with a diagnosis of CLBP with or without leg pain were recruited. A visual analogue scale (VAS) was used to measure low back pain intensity, and the Modified Oswestry disability questionnaire (MODQ) was used to measure functional ability. Plasma 25-OHD levels of all patients were measured and the prevalence of hypovitaminosis D was calculated. The multivariate logistic regression model was used to investigate the association between vitamin D deficiency and patient characteristics. RESULTS: A total of 328 patients were included in the study. Mean age of the study population was 43.8 years. Two hundred eighty-two (86%) (men 153/172 [89%], women 129/156 [83%]) of patients had below normal plasma vitamin D levels. Among these, 217 (66%) (men 126 [73%], women 91 [58%]) were found to be deficient and 65 (20%) (men 27 [16%], women 38 [24%]) were had insufficient levels. Multivariate regression analysis found that men were significantly more prone to have deficiency as compared to women (OR = 1.78 (1.10-2.88), P = 0.02). We also found a significantly positive relationship between vitamin D deficiency and increased functional disability (OR = 1.53 (1.24-1.87), P = 0.01). However, we did not find any relationship with pain severity, presence of other co-morbidities and educational level. LIMITATIONS: Not possible to access a good quality data on sun exposure and vitamin D dietary inake dieat in study population. No bone scans were performed. CONCLUSION: The result of this study provides a message about the high prevalence of hypovitaminosis D in the Indian CLBP population. Clinical guidelines for managing CLBP should include assessment of vitamin D status, together with advice on appropriate vitamin D supplementation in those found to be deficient. CLINICAL TRIAL REGISTRATION: CTRI/2014/03/004459.