Objective: To describe a case of bilateral simultaneous squamous cell carcinoma of the gingiva affecting the mandible in a lichen planus patient and discuss the pertinent literature. Method and Materials: We present a case of a 50-year-old woman with a history of oral lichen planus who was diagnosed with a primary and a second primary squamous cell carcinoma originating from the mandibular gingiva. A literature review did not disclose cases of gingival carcinoma arising simultaneously and bilaterally in the mandible. Results: Presentation of two simultaneous clinically distinct squamous cell carcinoma of gingiva, invading underlying mandible, is rare. Second primary tumor refers to a concomitant malignancy that is independent from the primary tumor. Second primary tumor is an independent prognostic factor since the surgical procedure is highly influenced by the extent of bony invasion. Conclusion: The general practitioner should be aware of the possibility of multiple independent lesions at different sites of the oral cavity. A thorough oral examination of sites remote from the obvious main lesion should be performed. The presence of simultaneous primary oral cancerous lesions may indicate a greater morbidity and a grave outcome for the patient. Keywords: gingiva, imaging, lichen planus, oral squamous cell carcinoma, second primary tumor, simultaneous