PurposeThe purpose of this paper is to explore the popularity of Japanese lesson study (JLS) beyond Japan and the challenges this translation might pose. It notes that there is not a universally accepted definition of lesson study (LS) and seeks to identify the “critical components” of JLS through a review of the literature. It then uses a systematic literature review of recent studies of the implementation of LS with in-service teachers beyond Japan to analyse the models of LS used against these seven critical components in order to explore the degree of fidelity to the Japanese model.Design/methodology/approachA broad review of the literature on JLS available in the English language identifies seven “critical components”. A systematic literature review of 200 recent English language studies of the implementation of LS with in-service teachers beyond Japan is then carried out. Articles published between 2005 and 2015 are explored, including peer reviewed articles, scientific journals, book chapters and PhD dissertations. This systematic review enables an analysis of the models of LS used in studies from beyond Japan against the “seven critical components” of JLS.FindingsThe analysis shows that there is not an internationally shared understanding of Japanese lesson study (JLS) and that many of the missing components are those which distinguish LS as a research process, not simply a collaborative professional development approach. It also reveals that UK LS models seem particularly far from the Japanese model in those critical components which connect teachers’ knowledge and understanding within groups, to knowledge and understanding that exists beyond it. The study discusses whether these differences could be attributed to structural or cultural differences between Japan and other nations.Research limitations/implicationsThe search for descriptions of the JLS is limited to articles available in the English language, which, therefore, represent a quite limited body of authority on the “critical components” of LS. The systematic review is similarly limited to English language articles, and there is a clear bias towards the USA, with the Far East and the UK making up the majority of the remaining studies. The study suggests that future research on LS beyond Japan should consider teachers’ attitudes towards the research elements of the process as well as their skills and confidence in carrying out research into practice.Practical implicationsThe study strikes a note of caution for schools wishing to implement JLS as an approach to teacher professional development in the UK and beyond. Japan’s systemic approach has embedded LS experience and expertise into the education system, meaning a uniform approach to LS is much more likely. In addition, other systemic challenges may arise, for example, UK professional development time and resources is not designed with JLS in mind and may therefore require a significant reworking.Originality/valueWhilst several systematic reviews of LS have explored its growth, geographical spread, impact and key features, this study provides a different perspective. It analyses whether and to what degree the “lesson study” models these studies describe align with the literature on JLS, and the implications of this for researchers and practitioners.