Gastrointestinal tumors pose a serious threat to human health, with their incidence and mortality rates accounting for more than half of all malignant tumors. Haptoglobin (Hp), an acute-phase glycoprotein, has been found to be elevated in both plasma and tumor tissues in various clinical conditions, particularly in different types of cancers such as liver cancer, gastric cancer, colorectal cancer, pancreatic cancer, and gallbladder cancer. Numerous studies suggest that Hp plays a significant role in the prognosis of cancer patients, highlighting its potential as a prognostic marker for gastrointestinal tumors with important clinical applications. Although research indicates that Hp is crucial in the development of various tumors, its specific mechanisms of action in gastrointestinal tumors remain controversial. Therefore, this paper reviews the differential expression and clinical significance of Hp in the five major types of gastrointestinal tumors, exploring its role in different stages of cancer progression and clinical prognosis. This aims to provide reliable and accurate serum biomarkers for the screening, early diagnosis, treatment, and prognosis monitoring of gastrointestinal tumors, which is of great significance for predicting the survival and prognosis of cancer patients.