The synchronous occurrence of tumors of different histological types in the stomach is uncommon. This rare association is usually detected incidentally at gastroscopy, surgery or histopathology. It is still not known whether such association represents an incidental coexistence or indicates a similar pathogenesis in the simultaneous development of tumors of different histological types in the same organ. A 73-year-old woman complained of discomfort after eating a Chinese dumpling, and had tarry stools three times. Gastroscopy showed a tumor at the juncture of the gastric fundus and corpus. The tumor was composed of gastric adenocarcinoma and gastrointestinal stromal tumor, in which the two components were intermixed with each other. To the authors' knowledge there are few reports of this extremely rare collision tumor association.