Aims: 1) Evaluate if the PICU Up! intervention, delivered under real-world conditions, decreases mechanical ventilation duration (primary outcome) and improves delirium and functional status compared to usual care in critically ill children; and 2) Conduct a multi-stakeholder, mixed-methods process evaluation to identify key contextual factors associated with delivery of PICU Up!. If proven effective, the PICU Up! intervention has potential to profoundly change medical care in the PICU and substantially impact public health by improving outcomes for the growing number of pediatric survivors of critical illness.