Lichen planus is a traumatic (koebner positive), chronic, inflammatory and autoimmune disease affecting the oral and genital mucosa, scalp and nails. The Food and Drug Administration approved the use of medical leeches for therapeutic purposes (hirudotherapy) in 2004 to ensure flap nutrition in plastic surgery. A 34-year-old male patient was admitted to our dermatology outpatient clinic with a swollen, itchy and purple-coloured rash on legs and back for a month, and white and reticulated plaques in the mouth. It was learned that a week earlier, eight leeches was applied to both knees and ankles to alleviate knee and leg pain. The patient had no history of drug use. A punch biopsy was taken from the patient with a preliminary diagnosis of lichen planus and lichenoid drug reaction. The histopathological examination showed hyperkeratosis, irregular acanthosis and hypergranulosis. Systemic methylprednisolone, levocetrizine and topical methylprednisolone aceponate were planned for the therapy. To the best of our knowledge, the appearance of lichen planus after hirudotherapy was never reported in literature. Hence, physicians should keep in mind that lichen planus and similar dermatoses could be triggered due to hirudotherapy. The fact that lichen planus appeared a week after hirudotherapy does not necessarily mean that leeches were the cause of this phenomenon. Accordingly, it could be deduced that lichen planus was probably developed as a result of leech therapy.