Parent behaviours and responses have been linked to children’s acute pain experience. However, parents’ internal experience, as assessed by physiological activity, in this context remains largely unknown. The current study primarily sought to examine: (1) parent cardiac response (heart rate [HR] and heart rate variability [HRV])) before and after their child’s experience of acute pain; (2) the relations between parent cardiac response and self-reported characteristics; and (3) the associations between parent cardiac response and child outcomes. Children and a primary caregiver (n = 23) participated in this laboratory-based pilot study. Parent HR and HRV were monitored at three different times: during a neutral video, immediately prior to the painful cold-pressor task, and following the cold pressor. Parent trait anxiety, typical emotion regulation strategies, negative emotional state, and state catastrophizing were examined. Child pain intensity, fear, and pain tolerance were assessed. Parents experienced changes in HR and HRV. Non-significant moderate effects were observed between parent HRV and reported traits. Parent HR was inversely associated with parent negative emotional state and differentially associated with child pain outcomes. Findings have implications for incorporating parent physiology in existing models of pain and parent-child interaction frameworks.