This book examines language teacher efficacy beliefs, focusing on the individual and collective beliefs of Japanese high school teachers. It discusses personal and collective dimensions of language teacher efficacy related to personal second language (L2) capability, instructional L2 efficacy and collective capability towards collaboration. The book provides a detailed discussion about the ways in which these beliefs develop and situates the findings within the wider field of teacher efficacy research. It helps further understanding of factors that may influence teacher self-efficacy and suggests new directions for research to explore in future studies. It will appeal to postgraduates and researchers with an interest in language teacher cognition, the psychology of language teaching and those in the wider fields of self-efficacy, teacher efficacy and teacher agency. It is also of use to those with an interest in the high school English education system in Japan, as well as researchers investigating similar contexts.