<![CDATA[Students’ limited ability to establish connections among mathematical concepts remains a persistent challenge, particularly in topics such as relations and functions that require coordination across multiple representations. While Problem-Based Learning (PBL) has been widely adopted, its effectiveness is often constrained by the lack of meaningful contextual grounding. This study aims to examine the effect of ethnomathematics-based PBL on students’ mathematical connection ability and to extend existing research by explaining how culturally contextualized problems support relational understanding. A quasi-experimental design with a pretest–posttest control group structure was employed, involving 99 eighth-grade students divided into two experimental groups and one control group. The experimental groups received ethnomathematics-based PBL, while the control group was taught using conventional PBL. Data were analyzed using non-parametric statistical tests, including the Kruskal–Wallis and Mann–Whitney tests, accompanied by effect size analysis. The results revealed significant differences among groups, with both experimental groups outperforming the control group. The large effect sizes (η² = 0.473; r = 0.75 and 0.69) indicate a substantial impact on students’ ability to coordinate symbolic, graphical, and contextual representations. These findings suggest that ethnomathematical contexts function as cognitive anchors that enable students to map real-world situations onto mathematical structures and reorganize relationships among concepts. This study contributes to the field by demonstrating that the integration of cultural context and structured inquiry not only improves performance but also strengthens the structure of mathematical understanding. Therefore, ethnomathematics-based PBL offers a theoretically grounded and practically scalable approach for enhancing relational thinking in mathematics learning. ]]>
