Background: Familyhistory of diabetes mellitus is a useful tool for detecting children and adolescents at risk of the disease. The aim of this study is to determine the prevalence and describe the characteristics of family history of diabetes mellitus in Nigerian children and adolescents with type 1 diabetes. Methods: A retrospective chart review of children and adolescents newly diagnosed with type 1 diabetes was conducted in three tertiary-healthcare institutions in Nigeria. In addition to the review of charts of old patients, other children and adolescents who presented with new-onset diabetes during the review process were also included. An interviewer-administeredquestionnaire was used in obtaining information from the patients and their parents. Using the criteria suggested by Scheuner et al, the family history risk category was stratified into average, moderate and high. Results: Out of a total of 65 children and adolescents with type 1 diabetes, 29(44.6%, 95% CI= 32.6-56.7) had a positive family history of diabetes mellitus. Of the affected family members, 42.9% were first-degree relatives. The frequencies of family historyrisk category were average 65.5%, moderate 27.6% and high 6.9%. Among the affected family members in whom information on their diabetes status was available, 19(86.4%) had type 2 diabetes and only 3(13.6%) had type 1 diabetes. Conclusion: Four out of every ten patients with type 1 diabetes in the paediatric age group, have a first-degree relative with a positive family history ofdiabetes.