This comprehensive study reviewed the literature on near-peer teaching (NPT) in higher education, synthesizing what is known from 111 empirical, peer-reviewed studies describing how near-peer teachers (NPTs) were trained, what instruction they provided, and the outcomes this yielded for students and NPTs. The vast majority of the studies was conducted in medical or science education and was often called peer-assisted learning, while a minority used supplemental instruction or peer-assisted study sessions. The training for NPTs focused on didactic skills, subject-matter knowledge, or both and was mostly offered before or before and during teaching. The instruction that NPTs provided was problem/case-based, practical, metacognitive, or a combination thereof, and was mostly part of a course. Both students and NPTs consistently evaluated the provided instruction and their experience as positive. The training and the instruction consistently resulted in improved learning outcomes for students and confidence in teaching skills, communication, and leadership for NPTs. The results indicate that NPT is a valued and promising practice in higher education, but a common theoretical model that structures and explains how specific combinations of training, instruction, and outcomes are related is noticeably absent. The current body of literature includes many descriptive and exploratory studies with a myriad of unstandardized outcomes. We present a theoretical model to explain the mechanisms of NPT and formulate practical guidelines for preparing and training NPTs.