OBJECTIVE: To describe lung ultrasound findings in children with respiratory failure on invasive mechanical ventilation (MV). METHOD: This is a longitudinal, observational, quantitative study conducted in the pediatric intensive care unit. Children with respiratory distress syndrome, aged between 6 months and 7 years, on invasive MV were included in the study. Lung ultrasound was performed using the BLUE protocol in the first 48 h of hospitalization and during ventilatory weaning. RESULTS: Seventeen patients who presented a significant reduction in A lines were included in the study. B lines showed worsening, indicating possible pulmonary complications. The decrease in pleural sliding from 14 to 3 (p = 0.04) and in the bat sign from 10 to 5 (p = 0.002) was statistically significant. The stratospheric sign showed a favorable trend (reduction from 3 to 0), but the p value of 0.08 was not significant. There was a moderate negative correlation between MV time and A lines, while a moderate positive correlation was observed between MV time and A lines. Furthermore, a moderate negative correlation between MV time and bat sign was also significant. CONCLUSION: It is indicated that bedside lung ultrasound is a valuable tool for monitoring and management of children on invasive MV, allowing the follow-up of critical pediatric patients during the hospitalization period.