The present research moved beyond focusing on negative dispositions to investigate the influence of positive aspects of personality, namely extraversion and openness, on stress responses including appraisals, affect and task performance. Challenge appraisals occur when stressor demands are deemed commensurate with coping resources, whereas threat appraisals occur when demands are believed to outweigh coping resources. We examined the unique influence of personality on stress responses and the mediating role of appraisals. Personality was assessed, and then participants (N = 152) were exposed to a validated math stressor. We found unique effects on stress responses for neuroticism (high threat and negative affect and low positive affect), extraversion (high positive and low negative affect) and openness (high positive and low negative effect and better performance). Mediation analyses revealed that neuroticism indirectly worsened performance, through threat appraisals, and that openness indirectly increased positive affect through lower threat. These findings highlight the importance of investigating multiple aspects of personality on stress responses and provide an avenue through which stress responses can be changed—appraisals. Only by more broad investigations can interventions be tailored appropriately for different individuals to foster stress resilience. Copyright © 2011 John Wiley & Sons, Ltd.