How do people come to know others' feelings? One idea is that affective processes (e.g., physiological responses) play an important role, leading to the prediction that linkage between one's physiological responses and others' emotions relates to one's ability to know how others feel (i.e., empathic accuracy). Participants (N = 96, 48 female friend pairs) completed a stressful speech task and then provided continuous ratings of their own (as "targets") and their friend's (as "perceivers") emotional experience for the video-taped speeches. We measured physiology-physiology linkage (linkage between perceivers' and targets' physiology), physiology-experience linkage (linkage between perceivers' physiology and targets' experience), and empathic accuracy (linkage between perceivers' ratings of targets' experience and targets' ratings of their experience). Physiology-experience (but not physiology-physiology) linkage was associated with greater empathic accuracy even when controlling for key potential confounds (random linkage, targets' and perceivers' emotional reactivity, and relationship closeness). Results suggest that physiological responses play a role in empathic accuracy.