Introduction: Low-grade polymorphous adenocarcinoma is a malignant neoplasm of salivary glands with uncommon occurrence in the head and neck region. The lesions occur more frequently among elderly females between the sixth and eighth decades of life, with a higher prevalence for the hard palate and soft palate. The most indicated surgical treatment is extensive surgical excision, including resection of the underlying bone. The purpose of this study is to describe a case report of a surgical excision of polymorphous adenocarcinoma in the maxilla with mucous flap reconstruction. Case Report: A 63-year-old male patient complaining of a tumor-like lesion in his left maxilla, which gradually increased in volume. At the intra-oral clinical examination showed the presence of upper and lower total dentures, an increase in volume in the left maxillary tuberosity region and a lesion of nodular features with fibrous and smooth consistency, fixed, sessile, oval shape, defined edges, and painless symptomatology. Radiographic imaging by panoramic radiography revealed a lesion with mixed radiographic density projected in the left maxillary tuberosity region and the in computed tomography scans were obtained and used for 3D image reconstruction. An axial tomographic view indicated the presence of a heterogeneous lesion with osteolysis: alteration in the cortical/trabecular bone and reabsorption of the left palatine bone, with regular contour and defined edges. Given the extent and complexity of the lesion, the surgical treatment in this case consisted of hemimaxillectomy and the surgery proceeded with mucosal flap reconstruction. The postoperative period followed was the service protocol, with no complications and no sign of recurrence. The pathological specimen was sent to the Anatomopathological Service, where the free margins and diagnosis were confirmed. Conclusion & Significance: The low-grade polymorphic adenocarcinoma is a rare malignant neoplasm that affects the salivary glands whose potential for malignancy, recurrence and metastasis are relatively low.