In skeletally mature patients, transverse maxillary deficiency poses a significant challenge due to the rigidity of craniofacial sutures. This technical note describes a minimally invasive, surgically assisted MARPE (sa-MARPE) protocol designed to overcome these limitations while avoiding complete Le Fort I osteotomies. The technique involves three small mucosal incisions and limited piezosurgical osteotomies targeting the midpalatal suture, canine pillars, and pterygomaxillary junctions. By preserving mucosal integrity and vascular supply, this approach reduces postoperative morbidity and enhances recovery. A case involving a 35-year-old woman treated with this protocol using a bone-borne expander (HIMAME) demonstrated stable skeletal expansion and crossbite correction at a 3-year follow-up, with no complications or relapse. This method offers predictable skeletal outcomes with minimal dentoalveolar side effects, making it a viable outpatient alternative to conventional SARPE in adults. Further studies are warranted to validate long-term stability and to compare outcomes with other assisted expansion techniques.