Delayed access to mental health services for children and adolescents has been linked to an increased risk of harm and nonattendance to scheduled appointments. While studies suggest that the lack of standardized assessments for prioritizing individuals has contributed to long wait times, the inconsistent use of assessments across service sectors in Ontario continues to persist. This has contributed to a paucity of information surrounding which children and adolescents may require urgent mental health services. Using a large secondary data set, this study examined whether service sector (e.g., school), and other individual client characteristics (e.g., age, sex, legal guardianship, interpersonal and school conflict) predicted greater mental health service urgency in 61,448 children and adolescents assessed using the interRAI Child and Youth Mental Health Screener. Binary logistic regression revealed that all predictors, except for sector, showed a significant effect on service urgency. Findings are instrumental in prioritization, reducing the likelihood that children with acute needs remain on waitlists.