Psychopathy is thought to be related to a lack of empathy which interferes with conscience development and promotes aggressive behavior. Little research has examined underlying mechanisms contributing to psychopathy, empathy, and aggression, such as an altered Hypothalamic-Pituitary-Adrenal axis response system. The current study examined how subscales of psychopathic personality traits, empathy, and aggression are related to the cortisol awakening response (CAR), an index of an individual’s physiological preparedness for the challenges of the upcoming day. A mixed-sex sample of 57 college students was recruited for the study, and HLM analyses tested whether these constructs were related to blunted CAR. Results indicated that Machiavellian Egocentricity, Blame Externalization, and Carefree Nonplanfulness subscales of the Psychopathic Personality Inventory – Short Form were all related to blunted CAR, whereas the Social Potency subscale was significantly related to steeper CAR increase. Further, affective empathy and reactive physical aggression were related to blunted CAR. Findings suggest that CAR provides a novel biological index of psychopathic personality traits, affective empathy, and reactive physical aggression.