Background and purpose: The prevalence of type 1 diabetes in all countries throughout the world is different. In this study, an introduction is, therefore, provided for the development of type 1 diabetes in children in Mazandaran province by using all available resources. Methods: In this descriptive cross-sectional study, the prevalence of patients with initial diagnosis of type 1 diabetes mellitus, aging from 6 months to 18 years, was located through contacting and referring to all organizations of insurers and doctors or experts in children endocrinologist and adolescent diseases in Mazandaran province. Results: 289 patients with type 1 diabetes were identified, 138 of whom were male (47. 8%), and 151 were women (52. 2%) with an overall prevalence of 0. 04%, and the rate of this prevalence was 48 cases among 100000 people (50 cases among 100000 girls and 36 cases among 100000 boys). The mean age of the patients was 11. 5 years old. In the study of delivery method, 180 patients (62. 3%) were diagnosed with cesarean section, and 109 (37. 7%) were born through natural delivery method. The mean age of onset of diabetes was 7 years. The minimum and maximum ages were 7 months and 18 years, respectively. 97 (33. 6%) of the patients were also hospitalized for the first time due to ketoacidosis, and were diagnosed with diabetes. Conclusion: Type 1 diabetes in Mazandaran province was more prevalent than the similar study in southern Iran and neighboring countries. It is essential to pay greater attention to this disease through studying it in the other parts of the country.