Mature defenses comprise one well-validated indicator of resilience. We investigated the relationships of resilience to trauma, attachment, temperament, cortisol, and cognitive performance in adult healthy volunteers. Participants were administered the Defense Style Questionnaire; the Relationship Questionnaire; the Childhood Trauma Questionnaire, and the Tridimensional Personality Questionnaire. Cortisol determinations included 24-h urinary, mean hourly plasma, response to low-dose dexamethasone suppression, and reactivity to the Trier social stress test (TSST). Mathematical performance during the TSST was quantified. Twenty-five women and 29 men participated. Resilience was significantly negatively correlated with childhood interpersonal trauma and with harm avoidance. Resilience was significantly positively correlated with urinary cortisol, secure attachment, reward dependence, and superior performance. In a linear regression analysis, the strongest predictor of resilience was childhood trauma, followed by math performance under stress and harm avoidance. We conclude that in young adults without manifest psychiatric disorder, resilience was associated with developmental, biological, and cognitive measures which merit further investigation.