Bullying prevention efforts have yielded mixed effects over the last 20 years. Program effectiveness is driven by a number of factors (e.g., program elements and implementation), but there remains a dearth of understanding regarding the role of school climate on the impact of bullying prevention programs. This gap is surprising, given research suggesting that bullying problems and climate are strongly related. The current study examines the moderating role of school climate on the impacts of a stand-alone bullying prevention curriculum. In addition, the current study examined 2 different dimensions of school climate across both student and staff perceptions. Data for this study were derived from a Steps to Respect (STR) randomized efficacy trial that was conducted in 33 elementary schools over a 1-year period. Schools were randomly assigned to intervention or wait-listed control condition. Outcome measures (pre-to-post) were obtained from (a) all school staff, (b) a randomly selected subset of 3rd-5th grade teachers in each school, and (c) all students in classrooms of selected teachers. Multilevel analyses revealed that psychosocial climate was strongly related to reductions in bullying-related attitudes and behaviors. Intervention status yielded only 1 significant main effect, although, STR schools with positive psychosocial climate at baseline had less victimization at posttest. Policies/administrative commitment to bullying were related to reduced perpetration among all schools. Findings suggest positive psychosocial climate (from both staff and student perspective) plays a foundational role in bullying prevention, and can optimize effects of stand-alone programs.