Understanding root canal morphology is one of the most important steps in successful root canal treatment. Thus, during the diagnosis and treatment phases of the maxillary molars, a clinician must be aware that anatomical variations exist. A number of studies, especially in vitro, have investigated various root canal morphologies, including aberrations of maxillary molars. This clinical case report highlights an unusual variant of a maxillary second molar with a third mesiobuccal canal.