Background: Communication and teamwork are critical non-technical skills in the operating theatre. However, prevention of events associated with communication failures by large simulation-based programs remains to be evaluated. The objective was to assess the impact of an interprofessional simulation-based training course on communication, teamwork, checklist adherence, and safety culture.Methods: We aimed to assess the impact of an interprofessional simulation-based training course on communication, teamwork, checklist adherence, and safety culture. We conducted a before-and-after interventional study based on a mixed-methods approach combining qualitative and quantitative evaluation criteria. The study was performed in a University Hospital with 39 operating theatres operated by 300 providers before (period 1) and after (period 2) an interprofessional simulation-based training course. Surgical procedures were observed, and the primary outcome measure was the rate of procedures with at least one communication failure associated with adverse event. Additional outcomes measured included the rate of other communication failures, checklist adherence, while teamwork and safety culture were assessed by questionnaires.Results: In total, 46 970 communication episodes were analysed during 131 (period 1) and 122 (period 2) surgical procedures. One hundred sixty-four professionals attended 40 simulation-based sessions. The rate of procedures with at least one communication failure associated with adverse events was not significantly different between the 2 periods (38% in period 1 and 43% in period 2; P = 0.47). Nevertheless, the rate of communication failures reduced between period 1 and 2 (8117/28 303 (29%) vs. 3868/18 667 (21%), respectively; P < 0.01). Teamwork scores and checklist adherence increased significantly after the intervention (8.1 (7.2-8.7) in period 1 vs. 8.6 (8.0-9.2) in period 2; P < 0.01 and 17% (0-35 %) in period 1 vs. 44% (26-57 %) in period 2; P < 0.01). Safety culture ratings did not change significantly.Conclusion: This study shows that although the rate of procedures with at least one communication failure associated with adverse event (primary endpoint) was not significantly different, a large interprofessional simulation-based training course has a positive effect on communication failures, teamwork, and checklist adherence.