Background: Some studies suggest that the SARS-CoV-2 pandemic increased the incidence of type 1 diabetes mellitus (T1DM) and diabetic ketoacidosis (DKA). However, the impact of this pandemic on pediatric T1DM is still mostly unknown. Therefore, we aimed to assess the effect of the COVID-19 pandemic on clinical outcomes in children with T1DM. Methods: We systematically searched for six databases up to 31 August 2022. We included 46 observational studies, 159,505 children of both sexes with T1DM, and 17,547 DKA events. Results: The COVID-19 pandemic significantly increased, in both sexes, the incidence of 1) DKA (OR 1.68; 95% CI 1.44–1.96), 2) severe DKA (OR 1.84; 95% CI 1.59–2.12), 3) DKA in newly diagnosed T1DM (OR 1.75; 95% CI 1.51–2.03), and 4) ICU admissions (OR 1.90; 95% CI 1.60–2.26). However, we did not find a significant association between this pandemic and 1) the incidence of T1DM, 2) the incidence of DKA in established T1DM, 3) the incidence of KDA complications, 4) the length of hospitalization stay, and 5) mortality. Subgroup analysis showed that the study design and the continent of origin accounted for the heterogeneity. Conclusions: The pandemic SARS-CoV-2 raised, in both sexes, the risk of DKA, severe DKA, DKA de novo, and ICU admissions.