Objective:To determine the glycemic control and cardio-metabolic complications of children and adolescents with type 1 diabetes mellitus (T1DM) attending a tertiary care diabetes clinic in Saudi Arabia.Methods:We conducted a retrospective cross-sectional study of children and adolescents with T1DM attending King Abdulaziz Medical City-Jeddah from 2010 to 2013. We assessed their glycemic control and diabetes management. Vitamin D status was compared with glycemic control and gender differences.Results:We identified 301 subjects (53.5% females); mean age was 13.9 ± 3.8 years. The mean duration of diabetes was 7.7 ± 3.7 years, body mass index (BMI) was 21.1 ± 4.5 kg/m2, and hemoglobin A1c (HbA1c) was 9.6% ± 1.9% in both genders. There were modest gender-specific differences in Saudi patients with T1DM, with males having more symptoms than females. Mean age at diagnosis of T1DM was slightly younger in males (6.01 ± 3.65 years) than in females (6.33 ± 3.45 years). Education was the most common reason for admission in males (32.9%), whereas diabetic ketoacidosis (DKA) was the most common reason in females (38.8%). Frequency of symptomatic hypoglycemic attacks was relatively higher in males (47.1%) than in females (42.9%). The majority of our patients (83%) were on intensive insulin regimen, having 4 injections or more per day. The remaining (17%) were on conventional insulin therapy. Only 26.2% had satisfactory HbA1c (⩽8%). The mean level of 25-hydroxyvitamin D was 35.15 ± 15.9 nmol/L and cholesterol was 4.75 ± 1.1 nmol/L. Vitamin D deficiency (25-hydroxyvitamin D ⩽ 37.5 nmol/L) was detected in 63.6% males and 67.7% females. No significant correlation between HbA1c and vitamin D deficiency was observed.Conclusions:Metabolic control among Saudi children with T1DM is less satisfactory compared with other countries. The high prevalence of vitamin D deficiency in this population supports the recommendation of vitamin D supplementation in T1DM subjects. Further studies in a larger cohort are needed to confirm our findings.