The occurrence of hypodontia (absence of teeth) and hyperdontia (presence of supernumerary teeth) in the same patient is a rarely seen condition in dental practice. Early diagnosis and adequate treatment are very important when addressing this abnormality in the mixed dentition. The approach will depend on the severity of the case and the timing of diagnosis. This paper reports the case of an 11-year-old patient with absence of the permanent maxillary lateral incisors and the mandibular second premolars, with concomitant presence of a supernumerary tooth in the region of the right mandibular lateral incisor. Based on physical and radiographic examination findings, a diagnosis of hypo-hyperdontia was made. The diagnostic and therapeutic management of the case is discussed. The treatment adopted was surgical removal of the supernumerary teeth and esthetic restoration to transform the permanent mandibular canines into lateral incisors.