Oral lichen planus (OLP) is one of the oral potentially malignant disorders. Although malignant transformation (MT) of OLP is relatively uncommon, periodic examinations are advisable to monitor for any changes related to MT. This case report presents a case of squamous cell carcinoma arising in a patient with gingival OLP and poor oral hygiene.The lesion was initially considered to be gingival swelling resulting from inadequate dental plaque control. However, it eventually transformed into oral squamous cell carcinoma.This case study discusses the risk factors for carcinogenesis and the importance of periodic regular observation.