Efforts to improve the quality of learning can be done through various approaches, one of which is lesson study. Lesson study is an activity for lecturers to be able to develop learning and professional skills so that they can realize the learning outcomes that have been formulated. This study uses a qualitative approach that aims to describe the effectiveness of lesson study in improving the quality of learning in cost accounting courses in the department of Economic Education FKIP Nusantara PGRI Kediri University. Descriptive analysis is used to describe the data obtained by the observer through observation activities during the learning process. Lesson study activities in learning cost accounting courses consist of three stages, namely: the planning stage (plan), the implementation stage (do), and the reflection stage (see). The results of lesson study activities show that: 1) The three stages of the lesson study-based learning process can increase the creativity and motivation of students and lecturers in cost accounting learning; 2) Lesson study-based cost accounting learning has formed a collaboration between lecturers, between students, and between lecturers and students so that it can create a pleasant and innovative learning climate; 3) Lesson study activities improve the quality of learning which is indicated by an increase in student performance both in the aspect of active involvement during the learning process and in creativity shown when given the task to design the order cost card (production).