This study reports the outcomes of a randomized controlled trial of Steps to Respect: A Bullying Prevention Program conducted in 33 California elementary schools. Schools were matched on school demographic characteristics and assigned randomly to intervention or waitlisted control conditions. Outcome measures were obtained from (a) all school staff; (b) a randomly selected subset of third-, fourth-, and fifth-grade teachers in each school; and (c) all students in classrooms of selected teachers. Multilevel analyses indicated significant (p < .05) positive effects of the program on a range of outcomes (e.g., improved student climate, lower levels of physical bullying perpetration, less school bullying-related problems). Results of this study support the program as an efficacious intervention for the prevention of bullying in schools.