In patients with obstructive sleep apnea (OSA) and epilepsy, the frequency of generalized spike and wave complexes (GSWCs) usually decreases after the initiation of nasal continuous positive airway pressure (nCPAP) therapy. However, we herein report a patient who had a transient increase in GSWCs following nCPAP treatment. A woman with epilepsy underwent polysomnography, who showed severe OSA and 30 GSWCs during the sleep study. Polysomnography at the introduction nCPAP showed that the GSWCs increased to 94 times during the monitoring period, despite improvement of her OSA. Polysomnography was again performed four months later, and the GSWCs had decreased to 23 times. Physicians should therefore be cautious regarding a possible increase in epileptiform discharges and seizures immediately after the introduction of nCPAP.