The current work was done to determine the correlation between vitamin D and cystatin C as a predictor of kidney disease in males with diabetes mellitus. A total of 60 males were taken from October to December 2018. They were divided into 30 patients with type 2 diabetes and 30 healthy volunteers' as a control group. Glycated hemoglobin HbA1c, plasma glucose level, creatinine and urea were measured for all subjects. Also, levels of 25(OH) D and cystatin-c were determined using the enzyme-linked immune sorbent assay method. In this current study, as expected, patients with diabetes mellitus had significantly higher (p< 0.001) fasting blood glucose (FBG), body mass index (BMI), and glycated hemoglobin (HbA1c) levels as compared to the age-matched controls group. In addition, a significantly higher increase in the average level of urea, creatinine, and cystatin-c while significant higher decreases in vitamin D concentration compared to the patients group with the control group were found. A significant negative correlation was found between 25(OH) D and urea levels. On the other hand, a significant positive correlation was observed between the 25(OH) D level and HbA1c, FBG, cystatin-c and creatinine. From the results of this work, vitamin D could be a valuable predictor of nephropathy in males with diabetes mellitus. Likewise, further work is required to suggest that vitamin D may be prone to nephropathy in all patients with diabetes mellitus by estimating cystatin C as a clinical risk for kidney function. Keywords: Nephropathy, cystatin C, vitamin D.