Background and Objectives: Reports of respiratory function in COVID-19 survivors are still rare, especially in children. This study aims to determine the prevalence and prognostic factors that influence long-term respiratory function in children after COVID-19. Materials and Methods: An observational analytical study with a retrospective cohort design was conducted between January and June 2024. The subjects were pediatric patients aged 5–18 years with confirmed history of COVID-19. Respiratory function was evaluated with spirometry. The analyzed prognostic factors included clinical classification of COVID-19, gender, age, comorbidities, history of ventilator support, history of hospitalization and persistent symptoms. Results: A total of 100 subjects were included in this study. The subjects were 53% female, 52% aged ≥ 12–18 years, and 76% had at least one comorbidity, the most common being obesity (27%). The majority (73%) had a history of mild COVID-19, and 78% were not hospitalized. The prevalence of impaired lung function was 47%, dominated by restrictive lung pattern. The prevalence of long COVID was 18%, with the most common symptom being fatigue (13%). The presence of persistent symptom is significantly associated with abnormal spirometry result (p = 0.03, RR 1.99; 95% CI 1.38–2.87). Undernourished status and moderate-to-severe and critical COVID-19 significantly influence long-term respiratory function with p = 0.002, aOR 5.64; CI 95% 1.89–16.85 and p = 0.006, aOR 5.18; and CI 95% 1.59–16.89, respectively. Conclusions: The prevalence of impaired lung function in children after COVID-19 was 47%. Persistent symptoms, undernourished status, and moderate-to-critical severity of COVID-19 were found to be associated with impaired long-term respiratory function in post-COVID-19 pediatric patients. Further prospective studies are needed to confirm these findings and clarify causal mechanisms. © 2025 by the authors.