Background and Objective: Critical thinking is one of the goals in higher education and a key element in students' mental health. This study aims to investigate the relationship between critical thinking skills with mental health and academic achievement of Qom University of Medical Sciences students. Materials and Methods: In this descriptive­-correlation study in 1394,a sample of 303students at Qom University of Medical Sciences were selected through stratified random sampling method with a view to gender.The data were collected through two standard questionnaires on critical thinking skills CCTST form(B) and mental health questionnaire of GHQ-28.Then the data were analyzed simultaneously using descriptive statistics methods, Pearson correlation and independent t-test, and multiple regression analysis. Results: Students’ mean score of critical thinking skills was (9.16 ± 3.15) which was interpreted as under average. The results of Pearson correlation test showed that there was no significant relationship between critical thinking skills and mental health (P=0.702, r=0.039) and academic achievement (P=0.284, r=0.081).There was also no significant relationship between mental health and academic achievement (P=0.141, r=-0.150). According to independent t-test results, there was no significant difference between male and female students’ average scores in critical thinking skills and mental health. But there was a significant difference between male and female students in academic achievement. Finally multiple regression analysis revealed that mental health and academic achievement did not predict any critical thinking skills. Conclusion: Considering that strengthening critical thinking in students and enhancing learning methods can improve learning skills and factors affecting their learning Therefore, by modifying and providing appropriate educational practices, critical thinking of students can be enhanced.