Lichen planus (LP) is an inflammatory disease that may involve multiple skin sites as well as mucous membranes, hair follicles and nails. It rarely occurs on the lips and usually then in association with oral lesions. We report a 43-year-old man with a 7-month history of inflammation and erosive lesions of the lower lip. Histopathological and immunofluorescence studies showed features of LP. Local treatment with betamethasone dipropionate 0.5% ointment led to complete resolution within 1 month. Four months later, the patient developed typical cutaneous LP. Isolated LP of the lip is unusual, although this condition may be underestimated and therefore under-reported in the literature.