This research aims to improve the learning outcomes of 3rd grade elementary school students in Catholic Religious Education subjects, especially the material "I am a Unique Personality", through the application of the Problem Based Learning (PBL) method. This Classroom Action Research (PTK) was carried out in two cycles with 5 students as research subjects. The research results showed an increase in the percentage of learning completion from 40% in the pre-cycle to 80% in the second cycle, as well as an increase in student learning activities from 60% to 100%. The application of PBL has proven to be effective in improving students' conceptual understanding, critical thinking abilities and problem solving skills in a small class context.