Action research in English language teaching has taken a central role in empowering English language teachers, as well as contributing to their professional development. It not only meets the needs of teaching practice but also enables research continuity in terms of a spiral process which includes planning, acting, observing, and reflecting. In the context of the Mekong Delta of Vietnam, however, there has been little documentation on issues relating to action research in English language teaching. As one of such attempts, this paper examines the perceptions of English teachers in the Mekong Delta about the role of doing action research to improve their teaching quality. The participants include 60 English teachers from 13 provinces in the Mekong Delta who have been trained in how to do action research. Data were collected with a 5-point Likert scale questionnaire and interviews. The findings of the study shed light on English teachers’ perceptions of action research in relation to their teaching improvement. Possible measures were also proposed to enhance further implementation of action research to improve English language teaching quality.