With the discovery of immune checkpoint molecules and the subsequent explosion of related research, immune checkpoint-blocking therapy has become a key topic in tumor immunotherapy. Immune checkpoint T-cell immunoglobulin mucin 3 (TIM-3) is a transmembrane protein belonging to the TIM family. It is expressed in a variety of immune cells and non-immune cells and is an important molecule for negative immune regulation. TIM-3 not only can reduce inflammation, mediate the immune tolerance of organ transplantation, and inhibit autoimmune disease, but also can cause tumor immune escape. Furthermore, it can activate negative immune regulation pathways by interacting with ligands and can inhibit the activation of immune cells to downregulate the killing effect of the immune system on tumors. By blocking the binding between TIM-3 and its ligand, the anti-tumor immune activity of immune cells can be restored, the size of tumor foci can be reduced, and the tumor clearance rate can be improved. This article briefly reviews the research on TIM-3 in tumor immunity and tumor immunotherapy conducted in recent years.