Mathematical communication ability refers to the capacity to express mathematical ideas or concepts using mathematical language, either orally or in writing. However, students’ mathematical communication skills remain generally low. One instructional approach that may enhance this ability is Problem-Based Learning (PBL). To increase student engagement in PBL, innovative teaching media such as GeoGebra can be integrated into instruction. This study aimed to examine the effectiveness of using the GeoGebra application within a PBL framework on students’ mathematical communication ability. A quantitative research design was employed, specifically a pretest–posttest control group design. The population comprised all eighth-grade students at SMP Negeri 1 Padangsidimpuan, North Sumatra, Indonesia. Two classes—VIII-F (experimental) and VIII-G (control)—were selected through purposive sampling. Data were collected using a mathematical communication ability test and a GeoGebra usage questionnaire. The Mann–Whitney U test was applied for statistical analysis. Findings indicated that students taught with GeoGebra-assisted PBL demonstrated significantly greater improvement in mathematical communication ability compared to those taught with conventional direct learning (DL). However, none of the students in either group achieved the minimum passing criterion (KKM). Furthermore, student responses to the GeoGebra questionnaire fell into the high category, suggesting a positive perception and favorable impact on the learning process. These results support the integration of dynamic digital tools like GeoGebra within student-centered pedagogies to foster mathematical communication.