Emergency departments should improve their preparedness for mass casualty incidents (MCIs) through periodic drills. These exercises are conducted while maintaining regular care. The aim of this study was to determine the impact of a disaster drill in a pediatric emergency department (PED) on real patients' waiting times. On September 10, 2019, a 4-h disaster drill was conducted in the PED of a tertiary pediatric hospital, with minimal staff reinforcement (2 nurses). Cases were real patients that came to the PED during the drill. The patients that visited the PED the day before were the control group. Variables analyzed were: age, sex, destination, triage level, time-to-triage, time-to-physician, length of PED stay, and percentage of patients visited within the optimal time according to triage level. Sixty-eight patients (case group) and 63 patients (control group) were analyzed; both groups were comparable except for the median age. There were no differences in time-to-triage, time-to-physician, and length of PED stay between the 2 groups. The percentage of patients visited within optimal time according to triage level was higher in the case group. Conducting an MCI drill in the PED, with minimal staff reinforcement, was not detrimental to real patients' waiting times.