Abstract Objectives To understand the international epidemiology of critical pediatric COVID-19 and compare presentation, treatments, and outcomes of younger (<2 years) and older (>2 years) children. Design Prospective, observational study from April 1 to December 31, 2020 Setting International multicenter study from 55 sites from North America, Latin America, and Europe. Participants Patients <19 years old hospitalized with critical COVID-19 Interventions none Main outcomes measured Clinical course, treatments, and outcomes were compared between younger and older children. Multivariable logistic regression was used to calculate adjusted odds ratios (aOR) for hospital mortality. Results 557 subjects (median age, 8 years; 24% <2 years) were enrolled from 55 sites (63% Latin American). Half had comorbidities. Younger children had more respiratory findings (56% vs 44%), viral pneumonia (45% vs 29%), and treatment with invasive ventilation (50% vs 37). Gastrointestinal (28% vs 69%) or mucocutaneous (16% vs 44%) findings, vasopressor requirement (44% vs 60%), and MIS-C (15% vs 40%) were less common in younger children. Hospital mortality was 10% overall but 15% in younger children (odds ratio 1.89 [95%CI 1.05-3.39]). When adjusted for age, sex, region, and illness severity, mortality-associated factors included cardiac (aOR 2.6; 95%CI 1.07-6.31) or pulmonary comorbidities (aOR 4.4; 95%CI 1.68-11.5), admission hypoxemia (aOR 2.33; 95%CI 1.24-4.37), and lower respiratory symptoms (aOR 2.83; 95%CI 1.49-5.39). Gastrointestinal (aOR 0.49; 95%CI 0.26-0.92) or mucocutaneous symptoms (aOR 0.31; 95%CI 0.15-0.64), treatment with intravenous immune globulin (aOR 0.33; 95%CI 0.17-0.65), and MIS-C (aOR 0.26; 95%CI 0.11-0.64) were associated with lower mortality. Conclusions We identified age-related differences in presentation and mortality for critical pediatric COVID-19 that should prompt more attention to improving management in younger children, especially in developing countries. Table of Contents Summary This is a multinational study describing critical pediatric COVID-19 clinical spectrum and related mortality in high and low-middle income countries during 2020. What’s known on this subject Pediatric critical illness due to COVID-19 is uncommon and have lower mortality compared to adults when hospitalized. While larger cohorts are from high-income countries (HICs), studies including data from low-middle-income countries (LMICs) remain scarce. What this study adds In our multinational cohort of critical pediatric COVID-19, we identified higher mortality than previously reported and age-related disease patterns. Children <2 years old had more respiratory disease and higher mortality, and older children had more non-pulmonary disease and better outcomes.