Medication errors are common in pediatric patients who require care from emergency medical services. This randomized trial measured the impact of a mobile app in reducing medication errors during simulated pediatric out-of-hospital cardiac arrest scenarios. Advanced paramedics were exposed to a standardized video simulation of an 18-month of child with cardiac arrest and tested on sequential preparations of intravenous emergency drugs of varying degrees of difficulty with or without mobile app support. Compared with conventional drug preparation methods, use of the mobile app significantly decreased the rate of medication errors and time to drug delivery.