To address obstacles of adopting lesson study at scale, this study investigated how a technology-assisted lesson study (TALS) approach could remove the obstacle of scheduling while retaining positive effects of traditional lesson study (LS). The TALS approach involves embedding lesson study within teachers' normal schedules, videotaping the research lessons using Swivl, and asychronously reviewing annotated videos of research lessons before debriefings facilitated by a mathematics specialist through Zoom. A TALS with two third-grade teachers was conducted. Analysis of the data, including lesson plans, research lesson videos, debriefing session videos and interviews with the teachers and the specialist, revealed that, as a traditional lesson study typically does, the research lesson was improved significantly. The participating teachers learned how to implement reform-oriented mathematics teaching through making critical alignments in sharpening learning goals, improving task design, and better orchestrating student work. Participating teachers and the specialist highlighted that the TALS provides teachers the opportunity to conduct LS without missing their own classes, examine student thinking in depth, and review and discus lessons critically. The unique contribution of the study is discussed.