<![CDATA[Critical thinking is one of the essential skills that needs to be developed at the elementary school level because it helps students understand, analyze, evaluate, and solve various problems. However, teacher-centered learning processes may limit students' involvement in critical thinking activities. This study aimed to determine the effect of the Problem Based Learning (PBL) model on the critical thinking skills of elementary school students at SD Negeri 075048 Lasara Siwalubanua. This study employed a quantitative approach using a quasi-experimental method with a Nonequivalent Control Group Design. The research sample consisted of 31 students, including 16 students from class V-A as the experimental group and 15 students from class V-B as the control group. The experimental group received learning through the Problem Based Learning model, while the control group received conventional instruction. Data were collected using a critical thinking skills test administered as a pretest and posttest. The data were analyzed using descriptive statistics, normality testing, homogeneity testing, an independent sample t-test, and N-Gain analysis. The results showed that the mean pretest score of the experimental group was 56.25 and increased to 82.50 in the posttest, while the control group increased from 55.67 to 70.00. The N-Gain score of the experimental group was 0.60, while that of the control group was 0.32. Both groups were categorized as having moderate improvement, although the experimental group demonstrated a higher increase. The independent sample t-test resulted in a significance value of 0.002 < 0.05, indicating that H₀ was rejected and Hₐ was accepted. Therefore, there was a significant effect of the Problem Based Learning model on students' critical thinking skills. Problem Based Learning can be used as an alternative instructional model to encourage students to actively identify problems, seek information, discuss, provide reasoning, determine solutions, and draw conclusions. ]]>
