This paper is a report on the outcome and significance of the international conference host by the Research Initiative for Developing Learning Systems (RIDLS) held on February 8th and 11th, 2016. Dr. Alicia R. Crowe and Dr. Mieke Lunenberg delivered keynote addresses on trends in the professional development of teacher educator and self-study methodologies. Following these addresses, the faculty and graduate students of Hiroshima University reported on their empirical case studies of the growth of teacher educators in Japan. In response, Toyokazu Imazeki, Nobuko Takeda, and Yu Kimura provided comments on the keynote addresses and case study reports from the perspectives of educational policy, research, and practice, and also gave their views on these topics. The significance of this conference was, first, that it was the first one that an international discussion on “teacher educators’ expertise” educator took place in Japan and, second, that the discussions identified many different viewpoints and arguments relating to “teacher educators’ expertise”. The conference elicited three aspects of tercher educator: (1) the ability to transmit educational research and practice, (2) the ability to carry out educational research and practices simultaneously, and (3) the ability to integrate educational research and practice with teacher education.