This study examines the impact of integrating GeoGebra software with the 5E instructional model on fifth-grade students' understanding of the formula for the area of a trapezium. This quasi-experimental research involved 90 fifth-grade students in southern Vietnam, divided into experimental and control groups. The experimental group received instruction through GeoGebra-supported 5E learning, while the control group was taught using traditional methods. Data were collected using pre- and post-tests to assess students' mathematical achievement. Results indicate a statistically significant improvement in the post-test scores of the experimental group compared to the control group, suggesting that the GeoGebra-supported 5E model effectively enhances students' comprehension and retention of the trapezium area formula. Qualitative analysis further revealed increased student engagement and positive attitudes towards mathematics in the experimental group. These findings highlight the potential of GeoGebra and the 5E instructional model in creating an interactive and student-centered learning environment that fosters deeper mathematical understanding. The study contributes to the growing body of evidence supporting technology integration in mathematics education and provides practical implications for educators aiming to improve student outcomes in geometry.