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This study aims to determine the effectiveness of the Problem-Based Learning (PBL) model in enhancing the mathematical communication skills and learning motivation of eighth-grade students at SMP Negeri 1 Padangsidimpuan. The research employed a quantitative approach with a quasi-experimental design, specifically the Nonequivalent Control Group Design. The study sample consisted of two classes: class VIII A as the control group and class VIII B as the experimental group, each comprising 28 students. The research instruments included a descriptive test to measure mathematical communication skills and a questionnaire to assess learning motivation. The results showed that the mean pretest and posttest scores for the control group were 47.58 and 50.00, respectively, while the experimental group obtained 46.73 and 83.04. The t-test results (p < 0.05) indicated a significant difference between the two groups, demonstrating that the PBL model had a positive impact on students’ learning outcomes. The N-gain analysis revealed a medium improvement category for both the control group (0.44) and the experimental group (0.54), with the experimental group showing higher gains. The implementation of the Problem-Based Learning model effectively enhanced students’ mathematical communication skills—particularly in representation, model formulation, and idea presentation—as well as their learning motivation, characterized by active participation, perseverance, and self-confidence. These findings highlight that PBL not only improves students’ understanding of mathematical concepts but also fosters deeper engagement and independent problem-solving abilities. Therefore, integrating PBL into mathematics instruction can serve as an effective strategy to develop both cognitive and affective aspects of student learning in secondary education.