Associations between autonomic nervous system health and cognitive performance have been described in different populations. Autonomic disturbances are a common phenomenon in patients post stroke. Little is known about the relationship between post stroke disturbances of the autonomic nervous system and the commonly occurring disturbances of cognitive functions revealed by victims of stroke. To assess the association between heart rate variability (HRV) and cognitive performance among patients post ischemic stroke and healthy age-matched controls, 13 patients post first-ever ischemic stroke aged 40-80 years and 15 age-matched healthy controls were evaluated. HRV was monitored during sustained handgrip, while breathing at a rate of six breaths per minute, while performing the serial-3 subtraction task sitting at rest, and while cycling. Patients post stroke had greater error rate in the serial-3 subtraction task, and lower HRV (both at rest and during task performance) relative to healthy controls (at rest 26 ms [10-53] vs. 43 ms [29-88]). The HRV of stroke patients showed less sensitivity to changes in testing conditions, and also failed to show the correlation with cognitive performance exhibited by the healthy subjects. Stroke patients experience autonomic nervous system dysfunction in parallel to their motor and cognitive impairments. Too often only the latter receive appropriate treatment consideration in the rehabilitation setting. The current results, and earlier research, point to the importance of focusing clinical attention to the status of the autonomic nervous system, as amelioration of its functioning is likely to enhance motor and cognitive functioning as well.