Copper is an indispensable trace element that participates in numerous metabolic and signaling processes in both its oxidized and reduced states. It is intimately associated with several facets of tumor development, and alterations in copper homeostasis can substantially influence processes such as tumor cell growth, metastasis, modulation of the tumor microenvironment, oxidative stress, cell signaling, and the evasion of tumor cells from immune surveillance. Copper metabolism in tumor cells predominantly promotes immune escape by regulating the expression of programmed death ligand 1. In view of its crucial role in tumor immunity, modulating copper metabolism has emerged as a prospective therapeutic approach. This paper reviews the regulatory mechanisms of copper within the human body and investigates how disruptions to copper metabolism impact tumorigenesis and progression, along with the immune and tumor microenvironments. We also discuss the research value of copper as a target for tumor immunotherapy, thus providing a theoretical basis for future research and clinical applications.