Oral lichen planus (LP) is a severe, painful form of LP, and is often resistant to topical corticosteroid therapy. Recently, open trials demonstrated that topical tacrolimus therapy was effective for the treatment of chronic erosive oral LP. We report two cases with severe recalcitrant erosive oral LP, who dramatically benefited from topical tacrolimus therapy. In case 1, a 64-year-old man presented with a 5-month history of painful erosions on his entire lower lip and buccal mucosa. Physical and histological examination confirmed a diagnosis of LP. He experienced rapid relief from pain and a dramatic improvement was obtained within 5 weeks of topical tacrolimus treatment. No significant irritation was observed and blood tacrolimus level was kept within a safe level (2.5 ng/mL). In case 2, a 68-year-old man developed painful erosions on his right lower lip and buccal mucosa 2 months before his arrival at our hospital. Histopathological analysis confirmed a diagnosis of oral LP. He experienced a rapid dramatic improvement of both lesions within 4 weeks of the start of tacrolimus application. No significant irritation or recurrence was observed. Thus, topical tacrolimus is suggested as a well-tolerated, effective therapy for oral LP.