Individual differences in stress reactivity and cognitive appraisal processes are thought to explain part of the heterogeneity in stress responses. This study investigated how perceived typical stress reactivity and momentary cognitive appraisal affect salivary cortisol responses to a laboratory performance stressor with social evaluation in 66 male non-smokers. Multiphase latent growth curve models showed positive associations of perceived stress reactivity and primary appraisal with cortisol responses. An age-adjusted path analysis suggested that primary appraisal mediated the effect of perceived reactivity to social evaluation on cortisol responses, and that effects of primary appraisal were attenuated at high levels of perceived reactivity. Our results suggest that individuals who report that they typically show strong perceived emotional, cognitive and autonomic responses to social evaluative stress tend to perceive the prospect of having to perform in front of an audience as more threatening, and that this appraisal then leads to stronger cortisol responses.