Lesson study developed organically in Japan over a period of 140 years, whereas in Indonesia, lesson study was introduced as a top-down initiative. This research explores beyond general cultural differences by illustrating how the daily concerns of teachers and their social interactions differ in Japan and in the case of an Indonesian school, the situation in the latter influencing how the Indonesian teachers engage in lesson study. This paper demonstrates through this comparison of contexts in two countries, how the approaches to teaching and professional development are influenced by sociocultural factors that are embedded in the teachers' lives, which are often beyond the scope of professional development programs. The differences in responsibilities of teachers, the nature of collegiality, and the pedagogic strategies of mathematics teachers are discussed in order to illustrate the engagement and challenges of lesson study in an Indonesian school.