Abstract: Monocarboxylate transporters (MCTs) are members of the solute carrier 16 (SLC16) family of proteins. They mediate the proton-linked transport of monocarboxylates, including lactate, across the plasma membrane. In recent years, studies have shown the association of MCT dysregulation with tumor progression in various types of solid tumors. MCTs were shown to participate in maintaining the hyper-glycolytic and acid-resistant phenotypes and the intracellular and extracellular pH levels of tumor cells by mediating lactate transport. In addition, lactate transport mediated by MCTs was shown to promote tumor angiogenesis and induce tumor immune tolerance. Therefore, in this article, we have reviewed research on lactate transport mediated by MCTs in tumors.