Introduction: Diabetic nephropathy (DN) is the most common cause of chronic kidney disease worldwide. A major challenge is to identify early diabetic nephropathy. microRNAs (miRNAs) are short noncoding RNA sequences and regulate a wide range of biological processes as cell differentiation, proliferation, cell metabolism and apoptosis. miRNAs may have a role in molecular mechanisms linked to cellular pathways of DN. The aim of this study was to investigate the level of microRNA 21 as a potential marker of early nephropathy in type 1 diabetes mellitus (T1DM). Methods: A total number of 340 participants were included and classified into 3 groups; Group I included 100 healthy participants, Group II included 120 patients with T1DM with 5 years duration. All participants were submitted to detail clinical examination, laboratory investigations, urinary albumin/creatinine ratio (ACR), estimated glomerular filtration rate (eGFR) as well as plasma microRNA 21 assays. Results: Blood pressure and ACR were significantly higher in group III than groups I and II. Further, microRNA 21 was significantly higher in group III than groups I and II, and more in group II than group I. microRNA 21 starts to rise in group II before microalbuminuria. miRNA 21 at a level of 0.01 had a greater sensitivity 94.1% and specificity 100% for identifying DN than ACR at level 45 mg/gm with sensitivity 88.2% and specificity 89%. Conclusion: Plasma microRNA 21 can serve as an early marker for diagnosis and identifying diabetic nephropathy in T1DM.