Dens invaginatus is a developmental dental anomaly resulting from invagination of the enamel organ into the dental papilla during odontogenesis, often leading to complex root canal configurations and challenging clinical management. This report describes the nonsurgical endodontic treatment of a maxillary central incisor with Oehlers type IIIa dens invaginatus associated with asymptomatic apical periodontitis. Diagnosis was established through clinical examination, periapical radiographs, and cone-beam computed tomography. Treatment involved combined instrumentation with Reciproc Blue, Self Adjusting File, and XP-endo Shaper systems, passive ultrasonic irrigation with 2.5% sodium hypochlorite and 17% EDTA, and calcium hydroxide as intracanal medication. The root canal was obturated with gutta-percha and epoxy resin-based sealer using a thermoplastic technique. Six-month follow-up showed satisfactory periapical healing. This case highlights the importance of accurate diagnosis and individualized treatment planning for the successful endodontic management of teeth with dens invaginatus.