Although many previous studies have reported the relationship between hypersensitivity and vagal function in children, the relationship in adults is unclear. This study investigates the relationship between hypersensitivity and vagal function, discomfort to sensory stimuli, and daily mood states in healthy adults. Using a questionnaire, 39 healthy adults were divided into hypersensitivity and control groups. We compared the baseline respiratory sinus arrhythmia (RSA), reflecting vagal tone and reactivity, subjective discomfort to sensory stimuli, and daily mood status between groups. Those in the hypersensitivity group had significantly lower baseline RSA and were more likely to experience greater RSA variability and discomfort during exposure to sensory stimuli than the control group. We found no significant difference between groups in daily mood status. These findings suggest that vagal function is an important marker of hypersensitivity in healthy adults.