Inflammatory myofibroblastic tumor (IMT) is a disease characterized by tumorous lesions consisting of myofibroblastic spindle cells and inflammatory cells that occur primarily in the soft tissues and viscera of children and young adults. Total excision is the most effective therapy. Steroids have been used to treat unresectable lesions with some success. We herein report a case of IMT involving the frontal bone accompanied by pachymeningitis. The tumor was characterized by an aggressive clinical course that was refractory to prednisolone. Performing total excision seemed difficult. Celecoxib and methotrexate were effective treatments. Our experience suggests the efficacy of celecoxib and methotrexate as alternatives for treating unresectable IMT.