A 13-year-old boy presented with clinical symptoms of periapical inflammation related to the right maxillary canine. A bizarre radiographic appearance of the root was considered suggestive of a compound odontome. Histological examination of the surgically extracted canine revealed a very rare variant of Oehlers' type 3 invagination. The invagination originated in a pit above the cingulum as a narrow coronal channel that opened into a large cavity inside the dilated root. The radicular part of the invagination contained all components of the attachment apparatus. The root canal and its apical foramen were slit-like and circular. Radiographic appearance of two roots separated by a wide interradicular area in a normally single-rooted tooth is indicative of this variant of type 3 invagination. Timely prophylactic treatment and follow-up or early endodontic treatment confined to the coronal channel are crucial to prevent pulp necrosis and consequent loss of the tooth.