Rationale, aims and objectives Aviation-based crew resource management trainings to optimize non-technical skills among professionals are often suggested for health care as a way to increase patient safety. Our aim was to evaluate the effect of a 2-day classroom-based crew resource management (CRM) training at emergency departments (EDs) on explicit professional oral communication (EPOC; non-technical skills). Method A pragmatic controlled before-After trial was conducted. Four EDs of general teaching hospitals were recruited (two intervention and two control departments). ED nurses and ED doctors were observed on their non-technical skills by means of a validated observation tool (EPOC). Our main outcome measure was the amount of EPOC observed per interaction in 30 minutes direct observations. Three outcome measures from EPOC were analysed: human interaction, anticipation on environment and an overall EPOC score. Linear and logistic mixed model analyses were performed. Models were corrected for the outcome measurement at baseline, days between training and observation, patient safety culture and error management culture at baseline. Results A statistically significant increase after the training was found on human interaction (β = 0.27, 95% CI 0.08-0.49) and the overall EPOC score (β = 0.25, 95% CI 0.06-0.43), but not for anticipation on environment (OR = 1.19, 95% CI.45-3.15). This means that approximately 25% more explicit communication was shown after CRM training. Conclusions We found an increase in the use of CRM skills after classroom-based crew resource management training. This study adds to the body of evidence that CRM trainings have the potential to increase patient safety by reducing communication flaws, which play an important role in health care-related adverse events.