English as a second language (ESL) teaching is partly a thinking process in which teacher knowledge plays a pivotal role in making instructional choices (Breen, Hird, Milton, Oliver, & Thwaite, 2001). The present study contributes to understandings of teacher knowledge by exploring the types of knowledge, which practicing teachers value in their teaching. Using course outlines from ESL teacher training programs, a Likert-­scale questionnaire was developed and delivered to 108 experienced ESL teachers in six states of Australia. Exploratory factor analysis of the data identified seven types of knowledge differently valued by ESL teachers--namely knowledge of practice, learners, resources and technology, curriculum, contextual factors, language learning theories, and language components. The overarching term for the first four used in the study is knowledge of teaching and the overarching term used for the last three is knowledge of language. Teachers regarded knowledge of teaching as significantly more important than knowledge of language.