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Autonomic dysfunction post-stroke negatively affects the cardiovascular system's ability to regulate heart rate and blood pressure response to exercise. While high-intensity interval exercise (HIIE) is prescribed for stroke recovery, limited knowledge exists regarding how HIIE impacts autonomic function post-stroke. Characterize autonomic nervous system response to HIIE post-stroke. Heart rate and blood pressure were recorded during a 10-min recumbent stepper HIIE bout, cool-down, immediately post-exercise, and 30-min post-exercise. Fast Fourier Transformation was used to determine low and high frequency beat-to-beat blood pressure and heart rate power spectral density at all timepoints and baseline baroreflex sensitivity. We tested for differences in spectral data between timepoints using Friedman's test. The influence of arterial stiffness, age, and beta-blocker use on autonomic function was explored using linear regression. Twenty-seven participants completed HIIE. The autonomic nervous system response to HIIE was blunted with neither low nor high frequency blood pressure or heart rate variability exhibiting significant changes from baseline during exercise (p > 0.05). Baroreflex sensitivity was impaired, with age (p = 0.03), arterial stiffness (p < 0.01), and beta-blocker use (p = 0.03) affecting sensitivity. Autonomic function is blunted during HIIE post-stroke and likely attributed to impaired baroreflex sensitivity and arterial stiffness.