Abstract: Tumor deposits were initially observed in colorectal cancer and subsequently in other cancers and had an important influence on the prognosis of patients. As an important histopathological characteristic in colorectal and gastric cancers, the eighth edition of UICC/AJCC Tumor–Node–Metastasis staging system for colorectal cancer classified tumor deposits without lymph node metastasis as N1c; those with lymph node metastasis were not included in the staging. In gastric cancer, although the significance of tumor deposits has been confirmed in several studies, their definition, origin, prognostic value, and effect on tumor staging remain controversial. Therefore, the effects of tumor deposits on clinical decision-making should be further explored. This study aimed to describe the recent findings on the prognostic value of tumor deposits and their influence on the staging and treatment of colorectal and gastric cancers, and emphasize their importance in prognosis prediction and treatment guidance of gastrointestinal cancer.