Autonomic signs and symptoms are a common feature of epileptic seizures. Although sympathetic activation responses are predominant, we can also find sympathetic inhibition and even an activation of the parasympathetic division of the autonomic nervous system, especially in partial seizures. These autonomic symptoms during seizures are thought to be the result of neuronal discharges arising from or spreading to cortical areas of the central autonomic network. Mydriasis, most commonly bilateral, is one of the most frequent findings. The patient described, a middle-aged man with a focal lesion in the right temporal lobe extended to the adjacent hypothalamus, presented with episodes of autonomic symptoms including prominent unilateral mydriasis, finally evolving into a state of decreased alertness. An ictal electroencephalogram and a simultaneous video recording supported the clinical impression of an epileptic aetiology. Unilateral mydriasis is a rare condition during epileptic seizures and very few cases have been reported in the past.