This study aimed to reveal the effect of teaching the 4th grade circumference measurement subject with the dynamic geometry software "GeoGebra" on achievement and motivation. In the research, the pre-test -- post-test control group design, which is one of the quasi-test designs, was used. In the Mathematics lessons conducted with the experimental group for three weeks, the subject of circumference measurement was taught with dynamic geometry software, whereas the control group followed the current curriculum. As data collection tools, the 21-item "4th Grade Circumference Measurement Achievement Test" (KR20=0.81) developed by Öksüz and Genç (2021) and the "Primary School Mathematics Motivation Scale" (KR20=0.94) developed by Ersoy and Öksüz (2015) were utilized. The pre-test was applied concurrently to the test and control groups one week before the research was initiated, and the post-test was applied immediately after the research ended. In the study, a paired-samples t-test was used to compare the pre-test and post-test scores of the students in the test and control groups within the groups; whereas covariance analysis (ANCOVA) was used to compare the post-test scores of the related groups. As a result of the research, it was concluded that there was a statistically significant difference between the achievement and motivation post-test scores of the students in the experimental group who learned the subject of "Circumference Measurement" with the dynamic geometry software and the students in the control group who did not use this program on behalf of the experimental group.