Children living in low socioeconomic communities are vulnerable to poor health outcomes, especially when critically ill. The purpose of this study was to investigate the association between socioeconomic status (SES) and illness severity upon pediatric intensive care unit (PICU) admission in children with acute respiratory failure. This secondary analysis of the multicenter Randomized Evaluation of Sedation Titration for Respiratory Failure clinical trial includes children, 2 weeks to 17 years old, mechanically ventilated for acute respiratory failure; specifically, subjects who had parental consent for follow-up and residential addresses that could be matched with census tracts (n = 2006). Subjects were categorized into quartiles based on income, with a median income of $54,036 for the census tracts represented in the sample. Subjects in the highest income quartile were more likely to be older, non-Hispanic White, and hospitalized for pneumonia. Subjects in the lowest income quartile were more likely to be Black, younger, and hospitalized for asthma or bronchiolitis, to have age-appropriate baseline functional status, and history of prematurity and asthma. After controlling for age group, gender, race, and primary diagnosis, there were no associations between income quartile and either Pediatric Risk of Mortality scores or pediatric acute respiratory distress syndrome. As measured, income-based SES was not associated with illness severity upon PICU admission in this cohort of patients. More robust and reliable methods for measuring SES may help to better explain the mechanisms by which socioeconomic affect critical illness.