Plasma cell gingivitis and cheilitis are diagnostic challenges for dental practitioners. To the best of the authors' knowledge, concomitant plasma cell gingivitis and plasma cell cheilitis in the same patient has not been reported in the dental literature, although these conditions have been reported separately (on lips and gingiva) several times. Underreporting of these coexisting clinical conditions may be attributed to a lack of awareness of both conditions and underperformance of comprehensive histopathological examinations. This article describes a case of plasma cell gingivitis with plasma cell cheilitis in a 63-year-old female patient. Histopathology and immunohistochemistry evaluations confirmed the diagnosis. After being informed about her condition and educated about possible allergens, which could be present in certain toothpastes, foods, and other foreign substances, the patient responded well to the stoppage of the use of suspected allergens. Identification and elimination of causative allergens is considered the accepted treatment for these conditions.