This prospective observational cohort study evaluated genetic, immunologic, and environmental factors associated with type 1 diabetes in children. Children with newly diagnosed type 1 diabetes and their healthy siblings were enrolled between October 2017 and June 2021. Data collection included HLA class I and class II genotyping, measurement of diabetes-associated autoantibodies to insulin (IAA), glutamic acid decarboxylase (GADA), insulinoma-associated antigen-2 (IA-2A), zinc transporter 8 (ZnT8A), and islet cell antibodies (ICA), as well as C-peptide and glycated hemoglobin (HbA1c). Healthy siblings underwent annual follow-up assessments for three years, while children with type 1 diabetes were evaluated every three months during the first year after diagnosis. Information on environmental risk factors was collected using an investigator-developed questionnaire based on anamnestic data. The study aimed to identify biomarkers and risk factors associated with the development and progression of type 1 diabetes in children.