The study aimed to describe the students' mathematical critical thinking skill in SMP Negeri 1 Bobotsari viewed from introvert and extrovert personality types. It was a qualitative study. The data were the students of class VIII H. The respondents were selected using purposive sampling technique. There were three respondents for each personality type. The data were collected using questionnaires, tests, interviews, and documentation. The data were analyzed using Miles and Huberman model including data reduction, data display and conclusion. The triangulation technique test was used as the data validation test. The results showed that the extroverted students have been able to analyze the problem with the logical reasons and have been able to be open-minded on finding the best alternative solution. However, they have not been able to solve a detailed and obvious problem and have not been able to conclude with the proper proof. While the introverted students have been able to analyze the problem with the logical reason, have been able to be open-minded on finding the best alternative solution. Furthermore, they have been able to solve the detailed and obvious problem and have been able to draw the conclusion with the exact proof.