The aim of this study was to compare the performance of the Paediatric Canadian Triage and Acuity Scale (Paed CTAS) to a previous triage tool with respect to the percentage of admissions, the diagnostic and therapeutic interventions, and the mean pediatric risk of admission (PRISA) score in a pediatric tertiary center emergency department. Data were prospectively collected for 4 months before the Paed CTAS introduction (PRE group) and for 4 months after its implementation (Paed CTAS group). Both groups were similar in chief complaints, distribution of triage levels, and mean PRISA score. In the Paed CTAS group, more patients were triaged in the higher acuity levels (53% vs 36%, P < .05), but the percentage of admission for these patients was comparatively lower (13% vs 27%, P<.05). The ability to predict admission was greater for the PRE tool as compared to the Paed CTAS tool (AUC: 0.82 vs 0.69, P=.001). The ability to predict requirements for interventions such as blood culture and intravenous fluid bolus was similar for both triage tools.