Purpose: The authors aim to determine the effects of Global Lesson Study (GLS) -- a two-year, one-cycle program defined as "international cooperative lesson study through international exchange among teachers using ICT" -- on intercultural competence for lesson study based on pre- and post-survey conducted for Japanese teachers. Design/methodology/approach: In accordance with the GLS program, mathematics lesson studies on mathematics between Japanese and Singaporean elementary school teachers were conducted over a two-year period. Questionnaire surveys on intercultural competence for lesson study was conducted using 7-point Likert scale and descriptive questions with Japanese teachers (N = 5). Analysis of Wilcoxon's signed rank test and correlation analysis were conducted. Findings: Followings are identified as the effects of GLS for Japanese teachers: (1) Japanese participants felt improvement of their competence in areas of attitude, internal outcomes and outward impact. (2) Participating in a GLS led to the improvement of Japanese teachers' qualities and abilities for subject teaching related to mathematics education. (3) Improvement of intercultural competence for lesson study was related to each other, and GLS led to improvement of these competences. (4) It was meaningful to have a two-year period to assimilate and adjust to independent experience of the host and guest. Originality/value: The GLS led to teacher empowerment among this sample, not only as cooperative research, but also at the individual level of teachers where participants continued to develop lessons based on the GLS learning after study completion. This has important implications for the implementation and dissemination of the GLS.