Solitary fibrous tumor (SFT) or hemangiopericytoma (HPC) is a rare fibroblastic tumor of mesenchymal origin. SFT or HPC comprises <1% of all primary central nervous system tumors. SFT or HPC of the sellar or suprasellar region is even more unusual. We herein report a sellar SFT or HPC in an octogenarian who achieved favorable progress with partial removal followed by fractionated gamma knife radiosurgery. An 87-year-old woman presented with occasional headache and visual field defects. A rapidly growing tumor of the sella turcica was diagnosed. The patient underwent endoscopic transnasal transsphenoidal surgery; however, only partial resection of the tumor was possible, as it was fibrous and hard with increased vascularity. A histological examination confirmed the tumor to be grade II SFT or HPC. Two months after the resection, the residual tumor grew rapidly. Given the patient's advanced age, re-surgery was not the preferred option; thus, fractionated gamma knife radiosurgery (marginal dose, 30 Gy in five fractions) was performed. MRI and visual field examination performed 3 months after irradiation revealed tumor shrinkage and improvement in the visual field, respectively. One year and three months after irradiation, the tumor continued to shrink and her visual field had improved. Taking age into consideration, partial resection with fractionated gamma knife radiosurgery was the more appropriate choice for both local tumor control and the safety of the optic apparatus.