Lacosamide is a new-generation antiseizure medication that is approved for use as an adjunctive treatment and monotherapy in focal epilepsy. Its use in generalized epilepsy, however, has not been adequately evaluated in controlled trials. We report a 67-year-old woman who experienced new-onset myoclonic seizures after initiation of lacosamide. We presume that she had an undiagnosed generalized epilepsy syndrome, likely juvenile myoclonic epilepsy. Myoclonic seizures were not reported before introducing lacosamide and completely resolved after lacosamide was discontinued. This suggests that lacosamide may have the potential to worsen myoclonus, similar to what has been reported with another sodium channel agent, lamotrigine, in some individuals with genetic generalized epilepsy (GGE).