A 75-year-old man was diagnosed with gastric cancer (UL post c0- II c (c T1N0) and M-less ctype II (cT2N0)) and rectal cancer (Rb ctype II (cT2N1) with multiple lung metastases (M1). The patient was treated with modified (m) FOLFOX6 regimen (oxaliplatin in combination with infusional 5-fluorouracil/Leucovorin). Chest and abdominal CT scan revealed that multiple lung metastases and abdominal lymph node metastases were obviously reduced in size. The primary lesion of the rectum almost disappeared on endoscopic examination. As for the lesions of the stomach, the UL post c0- II c lesion completely disappeared, and the M-less ctype II lesion was reduced remarkably. Thus, a significant reduction of the tumors was observed. This case suggests that mFOLFOX6 regimen can be an option for gastric cancer.