This study aims to determine the effect of the Project Based Learning (PjBL) learning model by using the Inquiry method on the concept comprehension ability of Grade VII students of O Mangunharjo Middle School in 2019/2020. The research method used is pure experimental form. 154 students and the sample is class VII.A as an experimental class and VII.E as a control class. Collecting data in research using tests in the form of a matter of description. Data collected were analyzed using t-test at the significance level α = 0.05. Based on the results of the t-test analysis at a significant level, it can be concluded that there is a significant influence on the Project Based Learning (PjBL) learning model by using the Inquiry method on the ability of concept understanding of seventh grade students of O Mangunharjo Middle School in 2019/2020. The average score of the ability of understanding the concept of the experimental class was 33.13 and the control class was 27.74. Keywords: Project Based Learning Model, Inquiry Method, Concept Understanding