Students' understanding of mathematical concepts is essential because by understanding the concepts, studentswill understand the subjects studied for a long time. This study aims to describe students' mathematical conceptsat SMP N 5 Purwokerto in terms of convergent or divergent thinking styles. The research method implemented was a qualitative descriptive method. The subjects of this study were students of grade IX H of SMP Negeri 5 Purwokerto in the 2021/2022 academic year. Data collection techniques employed were questionnaires, tests, interviews, and documentation. Meanwhile, the questionnaire used was a thinking style questionnaire. The test was utilized as an assessment to measure understanding mathematical concepts. This study indicated that: (1) Students' understanding of mathematical concepts was affected by students' thinking styles. (2) Convergent thinking style could not restate a concept, use the proper steps, solve problems carefully. (3) Divergent thinking style was unable to restate a concept, could use the proper steps, could not detect and correct errors in answers.