Learning-by-teaching is a pedagogical approach grossly underused in the education of engineers at all levels. The existing learning-by-teaching literature across all disciplines was reviewed with the intent of formally presenting this teaching method to engineering educators. The review defines learning-by-teaching, presents theoretical support for use, details the teaching process, and reports seminal work in a variety of contexts investigating the impacts on learning. The overall review is then discussed in terms of possible implications for engineering education.