Autotransplantation of a maxillary premolar tooth is a considerable option for tooth replacement in young adult patients, while Hemisection is a conservative way of preserving teeth. In this case report, we describe successful autotransplantation of the mesial root of the mandibular molar to replace the first maxillary premolar with complete root formation. The donor root was immediately placed at the recipient site and splinted for 14 days. Root canal treatment (RCT) was initiated 3 weeks after transplantation. Clinical and radiographic findings at 24 months of follow-up are compared with the results described in the literature. In case of non-extraction, adjacent teeth can be preserved in an economical way, also, case selection is essential in performing sequences of procedures for the success of treatment.