Purpose: The purpose of this exploratory study was to develop Global Lesson Study (GLS) defined as an international collaborative lesson study through international exchange of teachers using ICT. Its purpose is to nurture teachers from different countries with intercultural competence to conduct lesson study. Design/methodology/approach: We developed an initial program for GLS in the subject of mathematics education between elementary school teachers in Japan and Singapore. The qualitative analysis of activities at each stage of the Pilot GLS was conducted from two perspectives: (1) intercultural competence for lesson study; and (2) teacher's competency for subject instruction. Findings: Through GLS, a new lesson was created that was only possible with discussions from teachers from different locations. It was clarified that GLS was not only useful for training teachers with intercultural competence for lesson study but also has led to the improvement of teacher's competency for subject instruction in mathematics. Originality/value: The GLS is a new attempt in the sense of developing a high-quality lesson study method for creating new lessons as well as improving qualities and abilities of teachers through international exchange.