Background: diabetes in children is becoming an increasingly public health concern throughout the world. It is a chronic disorder of metabolism characterized by partial or complete deficiency of the insulin hormone. Self– cared diabetes involves a complex set of tasks and the key to successful management of diabetes is adherence to these tasks. Purpose: to evaluate the effect of mothers' care adherence on control of type 1 diabetes mellitus among their children. Design: A Quasi experimental design was used. Setting: It was conducted in Health Insurance Hospital of Shebein Elkom. Sample: purposive sample of 100 mothers admitted with their children having type 1 diabetes. Instruments: three data collection instruments were used; structured interview questionnaire, the Adherence in diabetes questionnaires and observational care practices checklist. Result: the current study demonstrated that there were high statistical significant differences between mothers' knowledge and practices on post intervention compared to pre intervention. As well, there were high statistically significant differences between mothers' adherence level on posttest compared to pretest at (p< 0.001). Conclusion: The study concluded that mothers of children with type 1 diabetes mellitus who adhere to diabetic care had effectively good glycemic control among their children on posttest compared to pretest. Recommendation: integration of health promotion program into school curriculum may enhance knowledge, practice, and mothers' adherence to care for their children with type 1 Diabetes Mellitus.