Background: Although medication adherence is important for diabetic children to prevent disease-related complications and improve quality of life, the rate of children adherence to therapeutic regimen is somewhat disturbing. Hence, this study aimed to assess factors affecting adherence toward therapeutic regimen among children with type 1 Diabetes Mellitus. Design: Descriptive exploratory design. Setting: This study was conducted at Diabetic Outpatient Clinic in Children's Hospital affiliated to Ain Shams University Hospitals. Sampling: A purposive sample comprised of 175 children with type 1 Diabetes Mellitus. Tools:I- Interviewing questionnaire; it was used to assess factors affecting adherence toward therapeutic regimen II-Morisky Scale: it was used to assess children' adherence to medication. Results: This study revealed that the mean age of studied children was 13.01±2.4yearsand slightly more than half of them were female. Most of studied children were adhered toward medication regimen and had agreement with beliefs toward therapeutic regimen. In addition, more than half of studied children had positive attitude factors toward adherence to therapeutic regimen, had social support factors to therapeutic regimen and did not have sufficient health care system factors. Conclusions: Attitude factors, social support factors, therapy factors, health care system factors and disease factors positively affected studied children' adherence towards therapeutic regimens. Meanwhile, beliefs factors and motivation factors did not have a significant effect on studied children' adherence towards therapeutic regimen. Recommendation: Continuous health teaching to children with type 1 diabetes to improve their adherence.