Background: Blended learning, defined as the combination of traditional face-to-face instructor-led learning and e-learning course, has never been validated as a teaching method for the effective use of manual defibrillators in cardiopulmonary resuscitation.Aim: To evaluate whether paediatric emergency and critical care providers exposed to a blended learning session performed better and recalled more defibrillator skills than those exposed to face-to-face learning only. Study design: A two-period prospective, stratified, single-centre, simulation-based, randomized, controlled trial. Methods: Registered nurses and postgraduate residents from either a paediatric emergency department or an intensive care unit were randomly assigned to a blended learning or face-to-face learning sessions on the recommended use of a manual defibrillator. Participants' adherence to recommendations was assessed by testing defibrillator skills in three consecutive paediatric cardiopulmonary scenarios performed on the day of the training and once again 2 months later. The primary endpoint was the number of errors observed during defibrillation, cardioversion, and transcutaneous pacing at the time of the initial intervention.Results: Fifty participants were randomized to receive the intervention and 51 to the control group. When pooling all three procedures, the median total errors per participant was lower (2 [IQR: 1-4]) in providers exposed to blended learning than in those exposed to face-to-face learning only (3 [IQR: 2-5]; P = .06). The median of total errors per procedure was also lower. However, both training methods appeared insufficient to maintain appropriate skill retention over time as a repetition of procedures 2 months later without any refresher learning session yielded more errors in both groups.