Physiological resonance between individuals is considered fundamental to the biological capacity for empathy. Observers of pain and distress commonly exhibit increases in reported distress, autonomic arousal, facial mimicry, and overlapping neural activity. An important, unstudied question is whether physiological stress can also resonate. Physiological stress is operationalized as activation of the hypothalamic pituitary adrenocortical (HPA) and sympatho-adrenomedullary (SAM) axes. People often report an aversive state resulting from the stress of another, but this could be conveyed through resonating arousal or distress, without activating the physiological stress response. Physiological stress is particularly important to examine since it commonly occurs chronically, with known negative effects on health. Salivary cortisol and salivary alpha-amylase (sAA) were measured in both speakers and observers during a modified Trier Social Stress Test (TSST) to assess activation of the HPA and SAM axes (respectively). Cortisol (but not sAA) responses resonated between speakers and observers. The cortisol response of observers increased with trait empathy and was not related to the speaker's subjective fear or distress. This study provides a novel method for examining physiological resonance, and indicates that we can indeed catch another's physiological stress, suggesting a specific health risk for those in the social network of stressed individuals.