Multiple primary malignancy is defined as two or more malignancies detected in an individual person. In particular, synchronous quintuple primary malignancy is extremely rare. A 52-year-old male with anal pain and intermittent blood-tinged stool was diagnosed with malignancies in the stomach, jejunum, ascending colon, transverse colon and rectum. He underwent a subtotal gastrectomy, segmental resection of the jejunum and total protocolectomy with end ileostomy. The postoperative pathologic findings were moderate differentiated gastric adenocarcinoma(pT1b N0M0, p StageⅠA), combined adenocarcinoma and neuroendocrine carcinoma of the jejunum(pT3N0M0, p StageⅡA), three mucinous adenocarcinoma of the ascending colon(pT3N0M0, pStageⅡA), transverse colon(pT1N0M0, p StageⅠ) and rectum(pT3N1 a M0, p StageⅢB). The tumors did not lack MLH-1 and MSH-2 expression, as the markers(bat26, D5S346, bat25, D2S123) suggest MSI-H presence. Adjuvant chemoradiotherapy was started according to regimen, FOLFOX 4 for advanced rectal cancer. Six years post-operation, the patient is currently attending regular follow-ups without recurrence or metastasis.