The purpose of this study was to analyze the effectiveness of the discovery learning-based mathematics learning module in terms of students' interest in learning mathematics. This type of research is quasi-experimental. The research design used was the One Group Pretest-Posttest Design. The research was conducted in class V SDN Ngijo 02 Gunungpati District, Semarang City. The number of students in the class is 28 students. The instrument used in the study was a questionnaire of interest in learning mathematics. Data analysis techniques used parametric statistical tests t-test and N-Gain. The statistical test results showed that the significance value was 0.00, meaning that the average score of students' learning interest after using the discovery learning model-based mathematics learning module was higher than the average score of students' learning interest before using the discovery learning model-based mathematics learning module. The average interest in learning mathematics in class V at SDN Ngijo 02 experienced an n-gain increase of 0.45 with the "medium" criterion. Thus, it can be concluded that the use of discovery learning model-based mathematics learning modules in learning has proven to be effective in increasing interest in learning mathematics for fifth-grade students at SDN Ngijo 02. Keywords: learning modules, mathematics, discovery learning, interest in learning