Background: Diabetic nephropathy is the leading cause of End Stage Renal Disease (ESRD) worldwide and a leading cause of Diabetes Mellitus related morbidity and mortality, which can be assessed by estimating Glomerular Filtration Rate. The early detection of renal dysfunction in subjects with diabetes is of vital importance as appropriate interventions have been shown to retard the progression of ESRD. We compared advantages of serum Cystatin C over Serum Creatinine for determination of early Decline in Glomerular Filtration Rate in Type ll Diabetes Mellitus Patients. Materials and methods: In the present study on 30 Type ll diabetic patients and 30 non-diabetic controls, we compared the estimated Glomerular Filtration Rate (eGFR) from serum Cystatin C and the estimated Glomerular Filtration Rate from serum Creatinine. Result: Estimated Glomerular Filtration Rate (eGFR) from serum Cystatin C was significantly decreased in patients as compared with eGFR from Serum Creatinine. Conclusion: Serum Cystatin C is a better parameter for assessing GFR In type ll Diabetes Mellitus for diagnosing early diabetic nephropathy than serum Creatinine.