Many managers adopt ‘toxic’ behaviors that create hostile work environments. How to prevent these behaviors remains unknown. We implemented CBT-oriented skills training for Bangladeshi garment factory supervisors, targeting behaviors that fuel hostility and aggression. Because psychologists delivering the training provided role models for respectful communication, by demonstrating concern for trainees, we compare treatment to both an active control group that received health advice from physicians and to pure control. Both interventions improved productivity, but only health training reduced toxic behaviors. Our results emphasize the need for active control groups and suggest that showing concern for managers may reduce aggressive behaviors.