This article presents a literature review in the field of mathematics teacher education research. The review focuses on identifying the main research trends in this field, that is, the main research topics that the mathematics teacher educators’ community is currently addressing, and the main theoretical concepts used to study these topics. One of the contributions of the review is that it identifies new research trends that have not been previously reported. Some of these trends are online mathematics teacher education, and the design and role of tasks in mathematics teacher education.