The field of teaching Chinese as a second language (CSL) is expanding and growing in importance worldwide. Related fields, such as Chinese language pedagogy, language policy, and the acquisition of Chinese as a second language, are attracting increased attention in research. However, research into K-12 CSL teacher cognition (what teachers know, think, and believe) has been very limited. It has been reported that more understanding of language teacher cognition has significant impacts on the development of teacher training and professional development programs (Borg, 2015; Kubanyiova & Feryok, 2015). Many aspects of CSL teacher cognition are underexplored when compared with language teacher cognition research in general and K-12 language teacher cognition research specifically. This article reviews current theoretical and empirical research into language teacher cognition with a particular focus on existing studies in the field of CSL teaching in the context of K-12 education. The purposes of the review article are (1) to document the current knowledge base of CSL teaching, and (2) to discuss current gaps in and future directions of teacher cognition research in this area. It first discusses general theories and research concerning second language teacher cognition within current research paradigms, and then provides a review of CSL teacher cognition research. Finally, it reviews pressing issues and suggests directions for future research in K-12 Chinese teacher cognition.