Students need critical thinking skills to develop their ideas in mathematics learning situations at school, and they can apply mathematical concepts in solving contextual problems. Junior high school students have unique characteristics and are highly curious about new knowledge. Therefore, it is crucial to apply the learning models that support the development of critical thinking skills. Problem-based learning is a student-centered learning model that familiarizes students with finding solutions to a problem. This study aims to see how applying the Problem-Based Learning model affects students' critical thinking skills. This type of research is a quasi-experimental conducted at one of the junior high schools in Yogyakarta in odd semesters of the 2022/2023 academic year using 2 subjects: a control class and an experimental class. The pretest and post-test were analyzed using the SPSS-assisted. The result shows that the N-gain score of students in the experimental class is 0,703 which is categorized as the high level, and the N-gain score of students in the control class is 0,417 which is in the medium level. This means that the Problem-Based Learning (PBL) model influences students' critical thinking skills more effectively than the conventional learning method. [For the complete proceedings, see ED672804.]