After 20 years of study since researchers of second language teacher education have increasingly emphasized the importance of investigating L2 teachers' mental lives, the research of language teacher identity has been flowering and providing intriguing insights to deepen the field's understanding of how L2 teachers develop and learn to become teachers. While a sociocultural perspective of language teacher education speaks to the situated nature of teacher learning and language teacher identity development, this perspective has generated a growing body of literature that highlights the role of socialization in language teacher identity formation. Reviewing the important ideas and findings in the existing research, this article begins with a summary of theoretical conceptualizations of language teacher identity, and then examines the status quo of contemporaneous language teacher identity research. Next, it discusses the socialization process in language teacher identity development, and ends with further research directions for future studies.