Introduction: Children are more vulnerable to cognitive impairment compared to adults due to ongoing brain development. Children with diabetes are at risk of developing various types of cognitive impairment. Objective: To assess the frequency of cognitive impairment among children and adolescents with type 1 diabetes. To assess the correlation between glycemic control and cognitive impairment among children and adolescents with type 1 diabetes (T1 DM). Methods: This cross-sectional study included 150 T1DM participants recruited from Pediatrics and Adolescents Diabetes Unit (PADU), Children's Hospital, Ain Shams University during the period from January 2023 to June 2023. Participants were divided into two groups according to diabetic control based on HbA1c. Neurocognitive function was evaluated in two groups based on glycemic control: those with well-controlled blood glucose levels (HbA1c < 7.5%) and those with poor control (HbA1c ≥ 7.5%). Assessments included the Wechsler Intelligence Quotient (WIQ), Benton Visual Retention Test (BVRT), and the computerized Wisconsin Card Sorting Test (WCST). Result: Children and adolescents with type 1diabetes who had poor glycemic control had significantly lower Total IQ (p<0.001), verbal IQ (p<0.001) and performance IQ(p<0.001) and disability at both visual memory and attention denoted by poor performance at BVRT also their score in WCST was poor in comparison to those with good glycemic control denoting disability in brain executive function. Conclusions: Participants with poor glycemic control type 1 diabetes (HbA1c ≥ 7.5%) had lower cognitive function, as well as deficits in visual memory, attention, and executive function, compared to those with good control type 1 diabetes (HbA1c < 7.5%).