"Lesson Study" and "Learning Study" are popular teacher professional development models across the world. Drawing on an extensive review of research and literature, this paper aims to identify the features of the two models to contrast and establish their similarities and differences particularly with regard to their application in practice. The paper focuses on their impact on teaching and learning as well as the rationale behind the process of "Lesson Study" and "Learning Study." Four major distinctions between the two models are revealed: ways of identifying a topic for teaching, views and methods for understanding student learning, the focus of teacher collaboration on lesson design and implementation, and the overall instructional design. The paper concludes that the two models appeal to different practitioners depending on their aims and objectives in teaching and learning as well as their broader perspectives on education. In addition, this paper suggests that the two models could complement each other to improve the effectiveness of teaching and learning in different contexts.