This research seeks to assess the enhancement of third-grade elementary students' understanding of mathematical concepts comprehension through the Team Games Tournament (TGT) instructional approach, supported by the PhET application, compared to traditional teaching methods. The study employs a quasi-experimental method using a nonequivalent control group design. A total of 63 third-grade students participated, selected through purposive sampling. Data were collected through multiple techniques, such as tests, observations, discussions, and photo and video records. The assessment tool used was a descriptive test measuring mathematical concept understanding and is stated to have met the requirements for content validity, construct validity, reliability, level of difficulty, and differentiation. The data analysis technique for hypothesis testing uses IBM SPSS Statistics 2.6 software, namely the normalized n-gain hypothesis test. As indicated by the research results, students' ability to understand mathematical concepts at SDN Pancasila Lembang experienced a significant increase after receiving learning using the Team Games Tournament (TGT) instructional approach supported by the PhET application. This is proven by the results of the n-gain data test calculation, which is 0.36 in the medium category. The posttest average score for the experimental group was 67.78 and the posttest average score for the control class was 30.32. This indicates that the improvement in mathematical concept understanding in the experimental group surpasses that of the control group. Consequently, it can be concluded that the Team Games Tournament (TGT) learning model, supported by the PhET application, is a recommended alternative for enhancing elementary students' ability to grasp mathematical concepts.