This Element aims to elucidate the theories of social cognition and to delineate their implications for the professional development of language teachers in primary and secondary schools.We first explore the concept of social cognition. The three key dimensions, that is, representation of social reality, social cognitive processing, and social mental abilities, of the social cognition theories are further elaborated with examples closely associated with language teaching and teacher development.We continue with more specific issues such as impression, attitude, emotion, and self-efficacy, which arise and develop as language teachers code, store, and retrieve information from social situations.We then discuss how social cognition influences teacher learning and development as observed and promoted within different social realities, and we end this Element with a call for a social-cognitive perspective on understanding language teachers' learning and development situated in diverse and changing contexts in and out of schools.