The general objective of this study seeks to examine the implementation of the Problem-Based Learning (PBL) model on students' critical thinking abilities in the topic of the human digestive system in Grade VIII at SMP State 1 Bulawa Junior High School. The specific objectives are: 1) to assess the implementation of the learning process, 2) to evaluate student activities, and 3) to gauge student responses when applying the PBL model to the topic of the human digestive system. The method used was an experimental method with a pre-experimental design in the form of a one-group pretest-posttest. The study's subjects were 24 students of Grade VIII at SMP State 1 Bulawa. Data collection techniques included written tests, observations, and response questionnaires, analyzed using descriptive quantitative analysis techniques. The results showed that the overall average percentage for the pre-test was 48%, categorized as less critical, while the post-test average was 73%, categorized as critical. This indicates that the implementation of the PBL model on the topic of the human digestive system can improve students' critical thinking abilities. The implementation of the learning process achieved an average percentage of 89%, categorized as very good. Student activities reached an average percentage of 74%, categorized as good, and student responses obtained an average percentage of 93%, categorized as very good. It can be concluded that the implementation of the PBL model in the topic of the human digestive system was well-executed, and students were actively engaged and received the learning process positively. Keywords: Problem-Based Learning, critical thinking, human digestive system