Purpose: The aim of this study is to determine the relationship between Beck Depression Inventory (BDI) and vitamin D levels, total and visceral fat mass in cancer patients. Methods: A total of 219 patients participated in this study. Patients' blood tests including prealbumin, vitamin D levels, BMI values and total and visceral fat masses were measured. Also, all subjects completed a self-administered BDI questionnaire. Obtained data were analyzed by using NCSS (Number Cruncher Statistical System) 2007 (Kaysville, Utah, USA). Results: A total of 219 patients consisted of 53.9% (n=118) females and 46.1% (n=101) males with median age 52.41 +/- 13.66 (range, 19-84) years. Mean BMI value was 24.70 +/- 3.75 kg/m(2); mean BDI score was 13.02 +/- 8.72; and mean prealbumin level was 0.21 +/- 0.07 g/L. BMI was negatively correlated with BDI in all study groups (P=0.002). Also prealbumin levels, vitamin D levels and hemoglobin levels were negatively correlated with BDI (P<0.05 for all). But no significant correlation was determined between total fat mass, visceral fat mass levels and BDI (P>0.05). Depression status had a significant relationship with BMI, vitamin D levels, prealbumin levels and malnutrition status in patients (P = 0.008, 0.001, 0.001, and 0.001, respectively). Conclusions: We have determined a significant correlation between vitamin D levels and BDI scores in cancer patients. Also prealbumin and hemoglobin levels may indicate BDI scores in cancer patients. There was no correlation between BDI score and visceral fat mass. There was a negative correlation between BDI score and BMI levels but no correlation was found between BDI score and total or visceral fat mass in cancer patients. Thus vitamin D levels could be used to determine the depression and nutritional status in cancer patients which may help to improve the clinical outcomes in those patients.