Introduction Necrotizing periodontitis (NP) is an atypical and painful form of periodontal disease, it is described by a promptly progress of ulceration and destruction of periodontal tissues; the NP is commonly linked to HIV‐positive patients. The aim of this report is to present a rare case of severe necrotizing ulcerative periodontitis treated non‐surgically. Case Presentation A 28‐year‐old dark skin female patient was referred to a dentistry college with the main complaint of spontaneous gingival bleeding and enlargement, oral pain during deglutition and dental hypersensitivity. Clinical and radiographic examination revealed generalized severe periodontal destruction, extensive bleeding, increased biofilm presence and spontaneous suppuration. Medical exams were requested, red and white blood cells were evaluated and among those exams an enzyme‐linked immunosorbent assay for HIV‐1 antibodies, the result reveled reagent to HIV‐1. The diagnosis of NP was assigned based on periodontal parameters such as necrosis and ulceration of the coronal portion of interdental papillae and gingival margin. Treatment established was scaling and root planning plus antibiotics. At 3 months of treatment the clinical and periodontal condition were stable. Conclusion This case report highlights a severe and generalized form of NP, where periodontal non‐surgical associated with antimicrobials resulted in elimination of the gingival enlargement, necrosis and ulceration of the coronal portion of interdental papillae and significant improvement of periodontal parameters.