Oral squamous cell carcinoma (OSCC) is the common malignant tumor in the oral cavity causing morbidity & mortality. Many types of tumors are found to develop due to chronic inflammation. Periodontitis and the bacteria colonizing the periodontal tissue may be associated with progression of tumors. Studies have reported the increase of anaerobic bacteria on the lesions of OSCC. Among various anaerobes, Porphyromonas gingivalis is one of the most important types of microorganism in the oral cavity present in both healthy and non-healthy individuals and it is involved in causing periodontitis. Chronic periodontitis may thus lead to the development of oral squamous cell carcinoma. This article reviews the literature on the association between P.gingivalis and Oral squamous cell carcinoma and the pathogenesis mechanism.