This study was conducted to examine the relationships between dispositional mindfulness, temperament, personality traits, and identity styles and to determine the predictive power of dispositional mindfulness, temperament, personality traits in identity styles. Methods: 223 students (120 females and 103 males) from the universities in Tehran were selected as the sample. The data were gathered using the Temperament and Character Inventory, the Mindful Attention Awareness Scale, and the Identity Style Inventory. Results: Dispositional mindfulness was significantly correlated with identity styles and identity commitment. There were also significant relationships between mindfulness and temperament dimensions and character dimensions (-0.32 to 0.38, P<0.01). Regression analysis indicated that three personality dimensions, i.e., self-directedness, self-transcendence, novelty seeking and dispositional mindfulness predict 35% of the variance of identity commitment; and dispositional mindfulness, self-transcendence, cooperativeness and novelty seeking predict 26% of the variance of normative identity style. Conclusion: The findings of this study indicate that mindfulness and the psychobiological aspects of personality may have a significant role in the process of identity achievement. Also, the biological aspects of personality may have a significant role in dispositional mindfulness.