The main purpose of the present study was to understand the relationship between mental health and the type and extent of irrational thoughts in Shahid Beheshti University students. Previous research has shown that mental health correlates with the extent and type of irrational thoughts. 385 students were selected for the sample group using relative classification random sampling. SCL-90-R and jones' IBT were administered. Pearson's correlation coefficient, t-test for two independent groups, and one way analysis of variance were used to analyze data. Results showed that the overall level of mental health in subjects significantly correlated with overall irrational thoughts. There were also negative correlations between mental health and demand for approval, high self expectation, frustration reaction, emotional irresponsibility, anxious overconcern, problem avoidance, and helplessness for change (P<0.000).A significant positive correlation was found with perfectionism (P<0.000). The main results of the present study are congruent with the findings of previous research.