Background: Previous studies have found simultaneous increases in skin conductance response and decreases in heart rate when normally fluent speakers watched and listened to stuttered speech compared with fluent speech, suggesting that stuttering induces arousal and emotional unpleasantness in listeners. However, physiological responses of persons who stutter observing stuttering and fluent speech has not been measured. Research suggests that the mechanism responsible for listeners' reactions is the mirror neuron system. The mirror neuron system activates when perceiving and producing goal-directed actions and forms the link between action perception and action production. Aims: To compare physiological responses elicited via fluent and stuttered speech in fluent and persons who stutter groups. Methods & Procedures: Participants included 15 adult persons who stutter (mean age = 29.7 years) and 21 normally fluent controls (mean age = 23.7 years). Participants watched and listened to six speech samples read by three persons who stutter speakers and three fluent speakers, while their skin conductance response and heart rate were recorded simultaneously. Participants' responses to each speech sample were defined as changes in mean heart rate and mean skin conductance response between 15 s before and 15 s during stimuli presentation. Outcomes & Results: Both groups showed similar patterns of response: skin conductance response was significantly increased and heart rate was significantly decreased in response to stuttered versus fluent speech. Similar to previous findings, the highest skin conductance response measures were induced by the first presentation of stuttered speech, with the response attenuating on subsequent presentations, while the heart rate was stable over time. Conclusions & Implications: Results confirmed past research that showed arousal and emotional unpleasantness when observing stuttering. Clinically, these results acknowledge the arousal and emotional discomfort in fluent speakers and persons who stutter. The physiological responses to stuttering and the underlying emotional aspects should be discussed in the therapeutic milieu with notions about coping strategies. (Contains 2 figures and 2 tables.)