In recent years, the synchronous occurrence of tumors of different histotypes arising in the same organ has been reported more frequently in the literature. In the stomach, adenocarcinoma has been described with coexisting primary rhabdomyosarcoma, carcinoid, and low-grade B-cell lymphoma of mucosa-associated lymphoid tissue. The simultaneous development of adenocarcinoma and gastric mesenchymal tumor has been documented rarely. We report one such case. A 65-year-old male was diagnosed with a proximal gastric adenocarcinoma and underwent subtotal gastrectomy. Subsequent histopathological examination revealed the presence of another tumor at the gastric antrum. This was a gastrointestinal stromal tumor of low risk category (GIST). The literature has only a few previous reports of this very rare association. It is not known whether this synchronicity is incidental or there is a causative factor inducing the development of tumors of different histotypes in the same organ. Pathologists, oncologists and surgeons should be aware of this interesting condition.