In Chapter 3, The Professional Development of the ESL Teachers, the authors present the background knowledge for understanding the discussion on the issues of teachers’ professional development. In this chapter, the authors discuss Leung’s (2009) concept of sponsored professionalism and independent professionalism in teacher professional development. The former is acquired through institutions while the latter is developed through social awareness of professionalism from the teachers themselves. The authors suggest that teachers should develop a balance of both sponsored and independent professionalism. Next, a discussion on teacher professional knowledge, factors influencing teacher’s knowledge and teacher learning was presented. A special reference to teacher professional development in Malaysia was made in order to provide the context of this study.