OBJECTIVES: To describe associations between the timing of tracheostomy and patient characteristics or outcomes in the cardiac ICU (CICU). DESIGN: Single-institution retrospective cohort study. SETTING: Freestanding academic children's hospital. PATIENTS: CICU patients with tracheostomy placed between July 1, 2011, and July 1, 2020. INTERVENTIONS: We compared patient characteristics and outcomes between early and late tracheostomy based on the duration of positive pressure ventilation (PPV) before tracheostomy placement, fitting a receiver operating characteristic curve for current survival to define a cutoff. MEASUREMENTS AND MAIN RESULTS: Sixty-one patients underwent tracheostomy placement (0.5% of CICU admissions). Median age was 7.8 months. Eighteen patients (30%) had single ventricle physiology and 13 patients (21%) had pulmonary vein stenosis (PVS). Primary indications for tracheostomy were pulmonary/lower airway (41%), upper airway obstruction (UAO) (31%), cardiac (15%), neuromuscular (4%), or neurologic (4%). In-hospital mortality was 26% with 41% survival at the current follow-up (median 7.8 [interquartile range, IQR 2.6-30.0] mo). Late tracheostomy was defined as greater than or equal to 7 weeks of PPV which was equivalent to the median PPV duration pre-tracheostomy. Patients with late tracheostomy were more likely to be younger, have single ventricle physiology, and have greater respiratory severity. Patients with early tracheostomy were more likely to have UAO or genetic comorbidities. In multivariable analysis, late tracheostomy was associated with 4.2 times greater mortality (95% CI, 1.9-9.0). PVS was associated with higher mortality (adjusted hazard ratio [HR] 5.2; 95% CI, 2.5-10.9). UAO was associated with lower mortality (adjusted HR 0.2; 95% CI, 0.1-0.5). Late tracheostomy was also associated with greater cumulative opioid exposure. CONCLUSIONS: CICU patients who underwent tracheostomy had high in-hospital and longer-term mortality rates. Tracheostomy timing decisions are influenced by indication, disease, genetic comorbidities, illness severity, and age. Earlier tracheostomy was associated with lower sedative use and improved adjusted survival. Tracheostomy placement is a complex decision demanding individualized consideration of risk-benefit profiles and thoughtful family counseling.