CONTEXT: Acute neurologic dysfunction is common in critically ill children and contributes to outcomes and end of life decision-making. OBJECTIVE: To develop consensus criteria for neurologic dysfunction in critically ill children by evaluating the evidence supporting such criteria and their association with outcomes. DATA SOURCES: Electronic searches of PubMed and Embase were conducted from January 1992 to January 2020, by using a combination of medical subject heading terms and text words to define concepts of neurologic dysfunction, pediatric critical illness, and outcomes of interest. STUDY SELECTION: Studies were included if the researchers evaluated critically ill children with neurologic injury, evaluated the performance characteristics of assessment and scoring tools to screen for neurologic dysfunction, and assessed outcomes related to mortality, functional status, organ-specific outcomes, or other patient-centered outcomes. Studies with an adult population or premature infants (≤36 weeks' gestational age), animal studies, reviews or commentaries, case series with sample size ≤10, and studies not published in English with an inability to determine eligibility criteria were excluded. DATA EXTRACTION: Data were abstracted from each study meeting inclusion criteria into a standard data extraction form by task force members. DATA SYNTHESIS: The systematic review supported the following criteria for neurologic dysfunction as any 1 of the following: (1) Glasgow Coma Scale score ≤8; (2) Glasgow Coma Scale motor score ≤4; (3) Cornell Assessment of Pediatric Delirium score ≥9; or (4) electroencephalography revealing attenuation, suppression, or electrographic seizures. CONCLUSIONS: We present consensus criteria for neurologic dysfunction in critically ill children.