Despite growing interest in L2 writing teachers, there is a dearth of published works that specifically delve into the nuances of the development of L2 writing teacher expertise. Informed by relevant foundational theory and empirical research, this book addresses this crucial gap in the understanding of expertise in L2 writing instruction. This book offers a holistic analysis of L2 writing instruction, serving as a valuable resource for those involved in the development of L2 writing teacher educators, as well as novice teachers striving to hone their skills in teaching L2 writing. It draws from a wide array of international perspectives on the conceptualization of L2 writing teacher expertise and research in this domain. Significantly, it is the first comprehensive work that places expertise in L2 writing instruction at the forefront. It will interest scholars in the disciplines of foreign and second language education, as well as postgraduate students and aspiring teachers.