Sleep deprivation in healthy adults has been associated with disrupted autonomic nervous system function, which in turn has been linked to cardiovascular health. High-intensity interval exercise (HIIE) may affect both sleep and cardiac autonomic modulation. Purpose: To investigate the impact of acute partial sleep deprivation on autonomic cardiac regulation before and after an acute bout of HIIE and the length of time for the autonomic system to return to resting levels. Methods: Fifteen healthy males with body mass index (BMI) of 25.8 ± 2.7 kg·m[superscript -2] and age 31 ± 5 y participated in a reference sleep ([approximately]9.5 hr) with no HIIE (RS), a reference sleep with HIIE (RSX), and an acute partial sleep deprivation ([approximately]3.5 hr) with HIIE (SDX). HIIE was performed in 3:2 intervals at 90% and 40% of VO[subscript 2] reserve. Autonomic regulation through HRV selected time and frequency domain indices were recorded the night before, the morning of the next day, 1 hr-, 2 hr-, 4hr-, and 6-hr post-exercise. Results: HIIE performed in a 3:2 W:R ratio decreased the HRV (p < 0.05) at 1-hr post exercise and it took up to 4 hr to return to baseline levels. Parasympathetic related HRV indices increased the morning of the next day for SDX (p < 0.05). Acute partial sleep deprivation and HIIE did not modify the HRV responses compared to reference sleep and HIIE. Conclusion: HRV disturbance typically seen in responses to an acute episode of HIIE is not influenced by acute partial sleep deprivation.