Data support the protective effects of human breast milk (HBM) feeding in acute illness but little is known about the impact of HBM feeding on the criticality of infants. To explore the relationship between early HBM feeding and severity of illness and recovery in critically ill children requiring intubation and mechanical ventilation for acute respiratory failure (ARF). Prospective cohort study of mothers of patients aged 1-36 months who participated in the acute and follow-up phases of the Randomized Evaluation of Sedation Titration for Respiratory Failure (RESTORE) clinical trial. Participants completed a survey describing HBM dose fed during their infant's first month of life. Of 138 patients, 70 (51%) received exclusive HBM feedings (90%-100% total feeds) and 68 (49%) did not. We found no group differences in severity of illness on paediatric intensive care unit (PICU) admission or severity of paediatric acute respiratory distress syndrome (PARDS) within the first 24-48 h of intubation/mechanical ventilation (Pediatric Risk of Mortality [PRISM] III-12 score median: 5 vs. 5, p = .88; moderate/severe PARDS: 53% vs. 54%, p = .63). While median time to recovery from ARF was reduced by 1 day in patients who received exclusive HBM feedings, the difference between groups was not statistically significant (median 1.5 vs. 2.6 days, hazard ratio 1.40 [95% confidence interval, 0.99-1.97], p = .06). Human breast milk dose was not associated with severity of illness on PICU admission in children requiring mechanical ventilation for ARF. Data support the protective effects of HBM during acute illness and data from this study support a clinically important reduction in time to recovery of ARF. Paediatric nurses should continue to champion HBM feeding to advance improvements in infant health.