: Lesson study is an approach to improve teachers' professionalism through collaborative learning and assessment based on the principles of sustainable cooperation and mutual learning to build a learning community. This study aims to know and to analyze any improvement in pedagogy and professional competence of early childhood teachers at the school by implementing lesson study, to find out teachers and principal's opinions about the implementation of lesson study activity at the school. This research is a quantitative research, pre-experiment method with the form of one-group pretest-posttest design. Research subjects; 21 early childhood teachers from XYZ school. Instruments used in this study are observation sheets and interview records. The data was analyzed by calculating the mean score from before and after the implementation of lesson study activity. The mean score then measured and categorized according to rating scales.This study found out that lesson study activities which consist of three steps; plan, do, and see, can improve teachers' pedagogical competence of early childhood education by focusing more on minds on learning activities, hands on, the use of local materials in everyday life (daily life). Lesson study activities were proven to improve the professional competence of early childhood teachers. Teachers develop, select and process good and meaningful material for learning creatively. Teachers and principle gave good response regarding the lesson study activity.