Introduction This case report describes the collaborative management of an extensive combined endodontic‐periodontal lesion related to a long palato‐radicular groove (PRG) on a maxillary lateral incisor. Cases with similar severity have been reported minimally in the endodontic journals but even less in the periodontal journals. This case report illustrates the result of multidisciplinary treatment of the combined lesions associated with PRG. Case Presentation A 63‐year‐old patient presented with a periapical radiolucency on tooth #10. After evaluation, the patient was diagnosed with an endodontic‐periodontal lesion associated with PRG. After being informed of a guarded prognosis, the patient consented to a surgical procedure in an effort to retain the tooth. Management of the case involved a combination of endodontic therapy, odontoplasty under dental operating microscopy to attempt to eliminate the root anomaly, and periodontal regenerative procedures with allografts and a resorbable barrier membrane. Clinical examination and the cone‐beam computed tomography scan at a 2‐year postoperative visit revealed a substantial reduction in probing depth and significant bone fill of the defect. Conclusions In the past, a long PRG in combination with a periapical lesion often resulted in extraction of the tooth. With accurate assessment of the etiology of the defect, patient education, and a multidisciplinary approach, teeth with a PRG may be retained with a stable outcome for years.