Although CAR has been regarded beneficial for English teachers, very few research explores such issue language teaching education context. The aim of this study is to investigate four EFL senior teachers' perspective involving in CAR projects with the researcher for one semester in an Indonesian school. It investigates how the teachers' engagement in CAR impacts on their pedagogical practice, and their perception of the support from the school and the researcher. This multiple qualitative case study explores the teachers' perspectives through in-depth interview, observation, and documents. Data were analysed using inductive approach. Using cross-case analysis, themes within and across the case were compared and grouped to get the findings of the study. The results of the study show that teachers' involvement in CAR brings meaningful impact on their teaching practice and their students. Despite little support gained from the school, teachers value the external support positively from the collaborator which motivates them to participate in CAR projects. This study contributes to the insight of promoting teachers engaging in action research through a collaborative mode. It also suggests that CAR can be an impetus tool professional development for teachers which impact on their pedagogy and personal growth.