A BSTRACT Introduction: Proteinuria is a common complication in patients with type 2 diabetic nephropathy (DN). The aim of this study was to evaluate the anti-proteinuria effect of active vitamin D in patients with type 2 DN. Methods: A double-blind randomized clinical trial study was conducted on 42 DN patients selected by convenience sampling method. After selecting patients based on inclusion criteria, they were randomly divided into control and intervention groups. Patients in the intervention group received 0.25 mg of active vitamin D per day for 12 weeks. The variables evaluated in the patients on the first day of the intervention included fasting blood sugar (FBS), calcium, phosphorus, creatinine, glomerular filtration rate (GFR), systolic and diastolic blood pressure, and proteinuria. These variables were also evaluated at the end of the first, second, and third month of intervention. Data were collected and analyzed in Statistical Package for Social Sciences software version 22. Results: Around 52.5% of the patients participating in this study were male and 47.5% were female. The mean age of the patients was 55.52 ± 6.58 years. The results of repeated measures analysis showed that active vitamin D significantly reduced proteinuria ( P = 0.000) in patients in the intervention group. The changes in FBS ( P = 0.235), calcium ( P = 0.393), phosphorus ( P = 0.694), creatinine ( P = 0.232), GFR ( P = 0.347), systolic blood pressure ( P = 0.615), and diastolic blood pressure ( P = 0.115) were not significant in patients in the intervention group. Conclusion: Prescription of active vitamin D can significantly reduce the incidence of proteinuria in patients with DN.