The solitary fibrous tumor (SFT) of peritoneum, especially arising in gastric serosa, is extremely rare. A case of SFT arising in gastric serosa of a 70-year-old man is reported. On abdominal computed tomography scan, an approximate 8.0 x 5.3 cm-sized solid mass with multiple nodular calcifications was noted in the omentomesentery of right upper abdomen, which was abutting to the gastric antral wall. At laparotomy the tumor was tightly attached to the gastric serosa and was completely excised by wedge resection of the stomach. The cut surfaces of the tumor were pale brown to pale yellow, firm, with multifocal yellowish, gritty, stony-hard nodules and cystic changes. Microscopically, the tumor was composed of mildly cellular benign-appearing spindle-shaped cells and bands of hyalinized collagen in varying proportions. The tumor revealed predominantly sclerosing pattern with extensive hyalinized fibrosis and multifocal dystrophic calcifications. The tumor was mainly located at the gastric serosa and subserosa, and its growth pattern was expansile with entrapping of muscularis propria and submucosa in the periphery of the tumor. By immunohistochemistry, the tumor cells were diffusely positive for CD34 and vimentin but negative for cytokeratin, desmin, smooth muscle actin, CD99 and c-kit. Although its occurrence is rare, SFT should be considered in the differential diagnosis of mesenchymal tumors of the stomach.