The present study aims to explore the effect of using dynamic mathematics software in a distance education environment on students' understanding of trigonometric functions. The sample of the study consists of 45 first-year students enrolled in two associate degree programs of a state university. In the research, the lessons in the experimental group were carried out in a distance education environment where synchronous and asynchronous education methods were integrated with the GeoGebra program, which is a dynamic mathematics software, and in the control group, in the traditional distance education environment without using the GeoGebra program. Both quantitative and qualitative approaches were used to analyze the data. The data were obtained from pre-test, post-test, and online interviews with students. The results revealed that the post-test scores of the students who used the dynamic mathematics software in the distance education process were significantly higher than the scores of the control group students. In addition, as a result of the online interviews, it was determined that the experimental group achieved a higher level of understanding in comparison to the control group.