This case study investigates the development of a 7-year inter-school elementary school English teachers’ professional learning community (PLC) in New Taipei City called MET inter-school PLC and teachers’ willingness toward participation, as well as their impact, roadblocks and strategies. Data were collected through interviews, participant observations of PLC activities, and document analysis. The five interviewees included two community leaders and three participant teachers who have been in this group for over five years. The findings of this study are as follows. 1. MET inter-school PLC includes various and customized operation practices and has been developing into a PLC of teacher autonomy. 2. Based on teachers’ professional development needs, various member sources, their effects, and social support from MET inter-school PLC, the participants have developed a high willingness towards sustained participation. 3. MET inter-school PLC has improved teachers’ professional development and learners’ achievement and also has positively influenced the participants’ schools. Moreover, some challenges for MET inter-school PLC were solved. Based on the research results, this study has proposed some suggestions to be put into use.