Background: Pediatric Intensive Care Unit (PICU) teams provide care for critically ill children with diverse and often complex medical and surgical conditions. Researchers often lack guidance on an approach to select the best outcomes when evaluating this critically ill population. Studies would be enhanced by incorporating multi-stakeholder preferences to better evaluate clinical care. This manuscript outlines the methodology currently being used to develop a PICU Core Outcome Set (COS). This PICU COS utilizes mixed methods, an inclusive stakeholder approach, and a modified Delphi consensus process that will serve as a resource for PICU research programs.