A safe, supportive school climate is critical for school effectiveness. Unfortunately, the research linking a positive school climate to critical student outcomes includes few systematic reviews of the school climate literature and no reviews focused on the effects of interventions to improve school climate. This review examined the methodological quality and findings from 18 experimental studies evaluating the effects of schoolwide interventions on teacher and student perceptions of school climate. Each study was rated in terms of quality of the methods and magnitude of effects on school climate. Results indicated that only three of the 25 articles were considered methodologically sound. Effect sizes estimating the differences in teacher perceptions of school climate ranged from -0.29 to 1.69, while those concerning differences in student perceptions ranged from 0.03 to 1.93. Studies examining the effects of schoolwide positive behavioral interventions and supports (SWPBIS) and social and emotional learning (SEL) interventions were the most methodologically sound and associated with the highest effect sizes.