This study examined the association between school climate and bystander responses to bullying. Participants included 26,176 secondary students (grades 8-12; 13,224 girls) from 76 schools across Western Canada, who were asked to complete a self-reported, district-wide, school-based survey. Results from a contextual effects model in a two-level multilevel modeling framework revealed that certain aspects of school climate significantly predicted different types of bystander behaviors. Specifically, greater student reports of school safety, adult support/respect, adult responsiveness, and adult/student acceptance of diversity predicted more active intervening behaviors. In addition, greater student perceptions of school safety, adult support/respect, and adult acceptance of diversity predicted less avoiding or neglecting behaviors. Interestingly, peer support, school belonging, student acceptance of diversity, and provision of opportunities were negatively related to seeking support from adults. This study underscores the unique and critical role of school climate on bystander behaviors among adolescents.