Aims & Objectives: Viral infections often cause acute respiratory failure (ARF) in children. While respiratory syncytial virus (RSV) is common, adenovirus (AdV) infections are known for their aggressiveness. Understanding clinical differences and outcomes is essential. This study compares clinical outcomes in Latin American pediatric patients with ARF due to severe AdV and RSV infections. We evaluate hospitalization duration, mortality rates, and new morbidities. Methods: We conducted a secondary analysis of the cohort registry in LARed, which includes pediatric patients across Latin American PICUs from April 2017 to December 2022. Patients were categorized by AdV or RSV infection. Competitive risk models and logistic regression were used, adjusting for significant factors. Results: The study involved 3,014 patients: 182 with AdV (6.0%) and 2,832 with RSV (94.0%). The median age was 3.9 months [IQR 1.8-86], with 62% males. Comorbidities were present in 32%, mainly prematurity. AdV cases had a higher pneumonia admission rate (29% vs. 17%, p < 0.01), older age (8.2 vs. 3.7 months, p < 0.01), and more comorbidities (42.7% vs. 32.2%, p < 0.01). RSV was associated with a shorter hospital stay (HR 0.74, 95% CI 0.61-0.89), while AdV had significantly higher mortality or new morbidities (aOR 6.15, 95% CI 2.78-13.57), after adjusting for age, bronchopulmonary dysplasia or chronic lung disease, and pneumonia diagnosis. Conclusions: AdV infection is linked to an extended hospital stay and significantly elevated rates of mortality or new morbidity compared to RSV in pediatric patients with ARF in Latin America. Keywords: Pediatric Intensive Care Units, Adenovirus Infections, Respiratory Syncytial Virus Infections, Respiratory Insufficiency, Infant Mortality