Aim: Acute apical abscess is caused by infection of the root canal and while it is initially related to the dentoalveolar region, it may spread to other areas and cause serious complications and extraoral swelling in cases where treatment is delayed. This case report aims to demonstrate the endodontic treatment management of a lateral tooth with an acute apical abscess with extraoral swelling that had previously been treated with endodontic treatment. Case Description: An 18- year-old female patient was admitted to our clinic with severe pain and intraoral and extraoral swelling. Intraoral examination revealed a swelling in the buccal gingiva of the upper right lateral incisor. Radiographic examination revealed root canal treatment and a large periapical lesion in the upper right lateral tooth. During dental anamnesis, the patient indicated that root canal treatment was performed in another clinic 3 years ago. It was decided to perform retreatment on the tooth with percussion and palpation sensitivity. In the first appointment, coronal restoration and previous root canal filling were removed and pus drainage was performed. After root canal obturation the access cavity was sealed and a nonsteroidal antiinflammatory was prescribed. In the second appointment, the pain and the swelling subsided and drainage ceased, calcium hydroxide was applied to the canal as a medicament. In the third appointment, the tooth was asymptomatic. The root canal treatment was completed using guttapercha and root canal sealer. The final restoration of the tooth was completed using composite, and the tooth was reviewed after one month. Results: In the follow-up appointment in the third month, the tooth was functional, without sensitivity to percussion and palpation. Conclusion: Successful clinical results can be obtained with the correct indication and effective treatment for teeth with extraoral swelling requiring retreatment.