Background: Type 1 diabetes is one of the most prevalent long-term diseases of childhood globally. Objective: This study aimed to evaluate a new biomarker such as preptin in patients with type 1 diabetes and to assess its relation to diabetic nephropathy. Patients and methods: This study was a case-control study that carried on 34 children and adolescents with type 1 diabetes mellitus in addition to 17 healthy children at the Pediatric Endocrinology Unit, Pediatric Department, Zagazig University Hospitals, from June 2020 to April 2021.All patients were subjected to laboratory investigations including fasting blood glucose levels, HbA1c, kidney function tests, lipid profile, serum albumin, urinary albumin, albumin creatinine ratio, glomerular filtration rate (GFR) and serum preptin. Results: This study showed that age, weight and BMI were significantly higher among group II with no significant difference between group I and II by LSD. Also, there was no significant difference among groups regarding gender or family history of DM. Conclusion: Serum preptin is significantly lower in patients with diabetic nephropathy compared with diabetic patients without nephropathy and healthy subjects.