Background/purpose: This research is motivated by the difficulties often experienced by students in adapting to their first year of college, especially related to learning calculus. To address these difficulties, a solution needs to be found so that these problems can be resolved. One solution that is expected to yield optimal results in addressing these issues is implementing self-explanatory learning by utilizing the GeoGebra application in studying integral calculus. Materials/methods: This study involved 25 first-year students enrolled in the Mathematics Education Program at the Faculty of Teacher Training and Education, Khairun University--the only public university in North Maluku Province, Indonesia. Given the institutional context, where only one relevant class was available, a quasi-experimental one-group pretest-posttest design was adopted. This design was selected due to practical limitations that precluded the inclusion of a control group. Despite this constraint, the chosen approach was considered suitable for assessing the impact of the intervention while adhering to ethical and logistical considerations in the research setting. Results: The results of this study indicate that the integration of GeoGebra into the instructional process significantly contributes to the enhancement of students' self-explanation skills. This is evidenced by a normalized gain score (N < g >) of 0.71, categorized as a high improvement. These findings suggest that GeoGebra effectively facilitates the strengthening of students' mathematical understanding through immersive visual interactions. Furthermore, the effectiveness of GeoGebra is demonstrated by an effect size value of 3.72, which statistically exceeds the threshold for a "large" effect. This result indicates that the learning intervention using GeoGebra has a very strong impact on improving self-explanation abilities. Such improvement is attributed to the learning process that leverages GeoGebra's dynamic, exploratory, and manipulable visualization features, thereby promoting more active cognitive and metacognitive engagement among students. Conclusion: Based on the data analysis results, the findings of this study indicate that learning by utilizing GeoGebra significantly helps students in developing and enhancing their self-explanation abilities. This technology provides students with opportunities to try new things, engage in independent exploration and visualization, and reduce their mental load in learning calculus during their first year at Khairun University.