OBJECTIVE Type 1 diabetes is associated with an increased risk of psychiatric morbidities. We investigated predictors and diabetes outcomes in a pediatric population with and without psychiatric comorbidities. RESEARCH DESIGN AND METHODS Data from the Danish Registry of Childhood and Adolescent Diabetes (DanDiabKids) and National Patient Register were collected (1996–2015) for this population-based study. We used Kaplan-Meier plots to investigate whether age at type 1 diabetes onset and average glycated hemoglobin (HbA 1c) levels during the first 2 years after onset of type 1 diabetes (excluding HbA 1c at debut) were associated with the risk of being diagnosed with a psychiatric disorder. Mixed-effects linear and logistic regression models were used to analyze HbA 1c, BMI, severe hypoglycemia (SH), or ketoacidosis as outcomes, with psychiatric comorbidities as explanatory factor. RESULTS Among 4,725 children and adolescents with type 1 diabetes identified in both registers, 1,035 were diagnosed with at least one psychiatric disorder. High average HbA 1c levels during the first 2 years predicted higher risk of psychiatric diagnoses. Patients with psychiatric comorbidity had higher HbA 1c levels (0.22% [95% CI 0.15; 0.29]; 2.40 mmol/mol [1.62; 3.18]; P < 0.001) and an increased risk of hospitalization with diabetic ketoacidosis (1.80 [1.18; 2.76]; P = 0.006). We found no associations with BMI or SH. CONCLUSIONS High average HbA 1c levels during the first 2 years after onset of type 1 diabetes might indicate later psychiatric comorbidities. Psychiatric comorbidity in children and adolescents with type 1 diabetes increases the risk of poor metabolic outcomes. Early focus on the disease burden might improve outcomes.