BACKGROUND AND OBJECTIVES: Iatrogenesis often results from performance deficiencies among medical team members. Team-targeted rudeness may underlie such performance deficiencies, with individuals exposed to rude behavior being less helpful and cooperative. Our objective was to explore the impact of rudeness on the performance of medical teams. METHODS: Twenty-four NICU teams participated in a training simulation involving a preterm infant whose condition acutely deteriorated due to necrotizing enterocolitis. Participants were informed that a foreign expert on team reflexivity in medicine would observe them. Teams were randomly assigned to either exposure to rudeness (in which the expert's comments included mildly rude statements completely unrelated to the teams' performance) or control (neutral comments). The videotaped simulation sessions were evaluated by 3 independent judges (blinded to team exposure) who used structured questionnaires to assess team performance, information-sharing, and help-seeking. RESULTS: The composite diagnostic and procedural performance scores were lower for members of teams exposed to rudeness than to members of the control teams (2.6 vs 3.2 [P =.005] and 2.8 vs 3.3 [P =.008], respectively). Rudeness alone explained nearly 12% of the variance in diagnostic and procedural performance. A model specifying information-sharing and helpseeking as mediators linking rudeness to team performance explained an even greater portion of the variance in diagnostic and procedural performance (R2 = 52.3 and 42.7, respectively). CONCLUSIONS: Rudeness had adverse consequences on the diagnostic and procedural performance of the NICU team members. Information-sharing mediated the adverse effect of rudeness on diagnostic performance, and help-seeking mediated the effect of rudeness on procedural performance.