The Early Childhood Education Quality (ECEQ) initiative is a pioneering approach toward supporting ongoing, self-organized professional development in the private kindergarten sector in Japan. The purpose of this study is to examine how kindergarten teachers and ECEQ coordinators experience this approach and view the ECEQ process. Online questionnaires were distributed to the teachers of 20 kindergartens that implemented the ECEQ for the first time in 2019 and to the ECEQ coordinators who supported them. The answers from 126 classroom teachers and 15 ECEQ main coordinators were analysed. Results indicate that: (1) almost all kindergarten teachers found the ECEQ experience meaningful; (2) teachers were resistant to holding open classes (work shadowing by colleagues from other kindergartens), but they nevertheless recognized the benefits; (3) teachers reported that the ECEQ enabled them to think about ECEC practices based on the children's perspectives; and (4) teachers reported that the ECEQ coordinators were supportive in terms of including teachers' ideas; however, they also felt that the ECEQ coordinators did not provide enough backing for autonomous meetings and in-house workshops after the ECEQ process had been completed. These results indicate both the strengths and difficulties associated with transforming the ECEQ into a system for supporting self-organized professional development.