Background and Aim: Research shows a strong relationship between psychological disorders and defense mechanisms; however, prediction of defense mechanisms has not been well investigated in normal samples. The present study intended to investigate the effect of big five personality traits in defense mechanisms used by university students.

Material and Method: In terms of data collection, the current study utilized a correlational descriptive research design. The population included all students of University of Tehran in 2015-2016 academic year. Using random sampling method, 170 individuals were selected and NEO-Personality Inventory and Defense Style Questionnaire (DSQ) were administered to them. To analyze the data, Pearson correlation coefficient and stepwise regression method were employed.

Results: The findings showed that Agreeableness and Extraversion predict mature defense mechanisms. It was also shown that Neuroticism and Conscientiousness are good predictors of immature defense mechanisms. In addition, findings demonstrated that Neuroticism and Agreeableness predict use of neurotic defense mechanisms.

Conclusion: It seems that personality traits play a great role in types of defense mechanisms used by university students; and this may be put into consideration in research and clinical settings.