Mucins are the most abundant high molecular weight O-glycosylated glycoproteins present in mucus. MUC13, a member of mucin protein family, is a membrane bound mucin. MUC13 has shown to be implicated in variety of gastrointestinal cancers including cancers of salivary glands (mucoepidermoid carcinoma), esophagus (esophageal squamous cell carcinoma), stomach (gastric adenocarcinoma), liver (intrahepatic hepatocellular carcinoma), pancreatic (pancreatic ductal cell carcinoma), and colorectal cancers (adenocarcinoma). In this review, we highlight the roles and implications of mucin MUC13 in various GI carcinogenesis. We also discuss the utility of MUC13 as diagnostic/prognostic indicators alone or in combination of other mucins/marker in GI cancers.