Continuous spikes and waves during slow wave sleep (CSWS) is rare and is considered to be an age-related epileptic syndrome occurring only in children. We report the case of a 21-year-old patient diagnosed with this syndrome. The patient had a history of seizures since the age of 3 and was admitted for continuous video/EEG monitoring to evaluate seizure exacerbation and unprovoked outbursts of anger. During 3 days of monitoring, awake EEG recordings showed focal slow wave activity in the right temporal region. CSWS were observed. After a change in his antiepileptic drug regimen, subsequent EEG recordings showed resolution of CSWS. As shown in our patient, CSWS can be observed in adults. In addition, continuous video/EEG monitoring including sleep is important in the evaluation of patients with sudden deterioration of seizure control accompanied by behavioral changes.