Abstract: The correlation between celiac disease (CD) and type 1 diabetes (T1D) mellitus has been known for decades. However, the data assessing celiac disease prevalence in type 1 diabetic patients among Arab population especially in Egypt were scarce. This study assessed celiac disease prevalence and its genotypic profile in Egyptian type 1 diabetic patients and their non diabetic relatives and determined effects of gluten-free diet on diabetes control and anthropometry. A total of 500 outpatients {15-49 years; with type 1 DM (300; F/M: 168/132) and their non diabetic relatives (200; F/M: 91/109)} and another 300 age and sex matched healthy control were randomly enrolled and screened for CD by tissue transglutaminase (TTG) antibodies, HLA genotyping and distal duodenal biopsy. The demographic, clinical, anthropometric data and effects of gluten free diet were assessed. CD prevalence was 10.3, 2 and 0.3% in T1D, relative and control groups, respectively. The majority of CD patients (77.42%) carried the HLA-DQ2 in linkage with HLA-DRB1*03 alone (41.9%) or with other alleles (DRB1*01,*04,*07,*08,*09,*13). Eleven patients (35.48%) carried HLA-DQ8 either alone in three patients or with other alleles (DRB1*03,*07 in five and three patients respectively. Only one patient with positive TTG-IgG and normal histopathology had negative DQ2 and DQ8 but positive DRB1*7 and *11 haplotypes. CD is a frequent but commonly under-diagnosed among Egyptian T1D patients. HLA-DQ2 and DQ8 genotypes (in linkage with HLA-DRB1*3 and HLA-DRB1*4 alleles) responsible for CD development are highly prevalent in Egyptian CD patients with T1D.