The objective of this Campbell systematic review is to examine the relationship between school-based law enforcement (SBLE) presence and school-related outcomes. The past several decades has witnessed a steady growth of the presence of SBLE around the world. There is no standard definition for SBLE, nor is there a common training, job description, or chain of authority. In the USA, the two most common approaches are to contract officers from a local law enforcement agency to work in the school, and school district police departments, in which the local school or district employs its own sworn police force. There is debate about whether SBLE is effective or harmful. This study synthesizes the empirical literature that examined the relationship between SBLE presence and school-related outcomes including: (a) crime and behavior problems; (b) perceptions of school; and (c) student learning.