The purpose of this study was to investigate the perception and practices of primary school English teachers on the role of lesson study (LS) in improving classroom practices in Bahir Dar City Administration, Ethiopia. To attain the purpose of the study, a mixed methods research approach with an embedded quasi-experimental design was used. Questionnaires, interviews, and observations were used to collect data pertinent to the study. Data collected through these methods were analyzed quantitatively using percentage, descriptive statistics, paired and independent sample t-test and qualitatively through description and narration. After 6 weeks of intervention, the results of the study showed that primary school English teachers' perceptions in LS and classroom practices have improved. The results also showed that those teachers who took part in lesson study performed better in preparing, enacting, and reflecting on their content plans. In addition, the paired sample t-test showed that there is a significant difference in mean value in the post-test (44.912) and the pre-test mean value (21.33), revealing that the post-test preferences are better. The independent sample t-test also showed a significant difference in the post-test results of the control and experimental groups. Thus, it is possible to conclude Lesson Study fostered collaboration work with colleagues improves teachers' competence.