Marginal gingivitis is a common form of periodontal disease that can be associated with human immunodeficiency viruses (HIV) infection. It is characterized by inflammation, bleeding, and plaque accumulation. We report a case of a 78-yearold male patient with HIV infection who presented with chronic marginal gingivitis and linear gingival erythema (LEG). The patient was treated with hydrogen peroxide mouthwash for 2-3 weeks. The gingival condition improved significantly after two weeks of treatment. This case illustrates the successful management of marginal gingivitis and LGE associated with HIV infection through non-surgical periodontal therapy and using hydrogen peroxide (1.5%) and chlorhexidine gluconate (0.2%) mouthwash alongside a systematic approach using anti-retroviral therapy.