OBJECTIVE To determine the association between vitamin D deficiency and breast cancer. METHODS This case control study included 94 female patients aged 20-75 years of any marital status and parity. Newly diagnosed 42 breast cancer patients who presented to surgical OPD of Dow University Hospital from Jan 2016 to June 2016 were included into the study as "cases" after informed consent. Age-matched 52 females who presented to OPD for complain other than breast pathology were included as the "control group". The sociodemographic of both cases and controls and histopathological characteristics of cases were recorded. Serum 25-(OH)2D levels were studied by the ELISA technique and recorded in ng/ml. Vitamin D deficiency was considered at serum level less than 20 ng/ml. RESULTS Mean age was 40.1 Years for controls and 47.6 Years for cases. Mean height, weight and BMI did not differ between cases and controls. Serum Vitamin D levels were significantly lower in cases (85.7%) than controls (55.8%). The unadjusted and adjusted ORs for breast cancer in cases and controls showed a statistically significantly increased risk of breast cancer with low vitamin D concentration (p value0.003). After adjustment for age, parity, BMI, sun exposure, economic status and education status the ORs (95% CIs) for breast cancer risk was7.8 (1.99 - 30.58) for women with vitamin D concentrations <20 ng/mL. CONCLUSIONS Findings of our study conclude that vitamin D deficiency is associated with risk of breast cancer.