This report describes a rare case of a supplemental tooth with a morfology similar to a lateral incisor, found in the canine region of the mandible of a 6-year-old male. The purpose of this paper is to report the importance of early diagnosis and treatment during mixed dentition. The treatment was extraction of the primary mandibular left canine soon after the initial diagnosis of the condition to facilitate the spontaneous eruption of the supplemental tooth and his removal. Twenty-nine months after the removal of the supplemental tooth the mandibular left canine was fully erupted into normal position. No complication arose from the presence of this supernumerary and his early diagnosis has been very important for not disrupting the normal erupting or alignment of other teeth.