Inflammatory pseudotumor (IPT) is a rare, locally aggressive, benign neoplasm of unknown etiology. It is uncommon in the head and neck region, particularly in the paranasal sinuses. We present an unusual case of IPT of the maxillary sinus and orbit in a 27-year-old woman who presented with cheek swelling, right orbital swelling, double vision, and associated fever and trismus. Computed tomography identified a mass with radiologic features suggestive of a malignancy of the maxillary sinus and orbit; the mass extended into the infratemporal fossa, parapharyngeal space, anterior antral wall, and surrounding soft tissue. A diagnosis of IPT was established on the basis of histologic and immunohistochemical analysis, which identified a proliferation of bland spindle cells and a mixed inflammatory cell infiltrate. Despite its aggressive appearance, IPT is associated with a good prognosis. Our patient was treated successfully with a combination of surgery, steroid therapy, and methotrexate. Chemotherapeutic agents are generally reserved for recalcitrant cases.