Content and Language Integrated Learning (CLIL) enables students to learn subjects through a language other than their native tongue. Widely researched and implemented, especially in the European Union, CLIL has shown benefits in language acquisition, exposure to a second language, and motivation since its emergence in the 1990s. This chapter provides a systematic review of CLIL-related teacher education research, examining articles from 2010 to 2020 using databases like Web of Science, ERIC, and Scopus. The focus is on pre-university education, as CLIL has mainly been applied in primary and secondary schools, while English Medium Instruction (EMI) is more common at the tertiary level. The review covers research focus, contexts, methodologies, and conclusions, highlighting research gaps and offering insights into future directions for CLIL teacher education.