ABSTRACT Tryptophan (Trp) is an essential amino acid that serves as a precursor for the synthesis of several important bioactive compounds. Trp is involved in a variety of pathophysiological processes, including neuronal function, metabolism, inflammatory responses, oxidative stress, immune regulation, and intestinal homeostasis. The role of Trp metabolism in tumorigenesis and cancer progression is of particular significance. The influence of Trp and its metabolites on tumor growth and metastasis is mediated through various mechanisms, such as immune evasion, promotion of angiogenesis, and increased resistance to therapeutic agents. This review presents the physiological pathways involved in Trp metabolism and its implications for various malignancies. We also highlight the latest clinical research targeting Trp metabolic pathways in oncology, in addition to exploring future directions for therapeutic advancements aimed at modulating Trp metabolism to enhance cancer treatment outcomes.