This study investigated how involving in a lesson study process at virtual settings impacted participating teachers' knowledge. The two elementary mathematics teachers, teaching in two public elementary schools at distant cities and meeting occasionally face to face and regularly at virtual settings formed the sample of this study. Neither of the teachers had any math teacher collegue they can collaborate in improving their instruction or their own knowledge. Teachers developed seven reform-based math lesson plans during one semester of a school year. They followed every step of lesson study, except they had to adapt the observation phase due to long distance between them. The teachers could not observe each other's teaching. They had to rely on the reflections of their colleagues about how the lesson went at the observation stage. The data were collected through teachers written responses to three open ended questions and written reflections after each math lesson. The data is categorized based on the commonalities of teacher statements. The results of this study suggest that lesson study is an effective professional development model in improving their knowledge even for the teachers who cannot talk face to face and observe each other's classroom. (Contains 3 tables.)