Both heat stress and vestibular activation alter autonomic responses; however, the interaction of these two sympathetic activators is unknown. To determine the effect of heat stress on the vestibulosympathetic reflex, 8 subjects performed static head-down rotation (HDR) during normothermia and whole-body heating. MSNA (MSNA; peroneal microneurography), mean arterial blood pressure (MAP), heart rate (HR), and internal temperature were measured during the experimental trials. HDR during normothermia caused a significant increase in MSNA (5±1 bursts/min; 53±14 arbitrary units/min), while no change was observed in MAP, HR, or internal temperature. Whole-body heating significantly increased internal temperature (0.9±0.1 °C), MSNA (10±3 bursts/min; 152±44 arbitrary units/min) and HR (25±6 beats/min) but without altering MAP. HDR during whole-body heating increased MSNA (16±4 bursts/min; 233±90 arbitrary units/min from normothermic baseline), which was not significantly different than the algebraic sum of HDR during normothermia and whole-body heating (15±4 bursts/min; 205±55 arbitrary units/min). These data suggest that heat stress does not modify the vestibulosympathetic reflex and both the vestibulosympathetic and thermal reflexes are robust, independent sympathetic nervous system activators.