Since the rapid development of nanomedicine in oncotherapy, multiple nanomaterials are adopted to regulate the immune system in cancer individuals. Tumor immunotherapy enhances the immune function of patients to achieve the purpose of killing tumor cells by utilizing the organism immune mechanism. As emerging inorganic carbon nanoparticles, carbon dots (CDs) have been found as photosensitizers, vaccines, immunoadjuvants, and so on for cancer treatment due to their unique structure and property, such as effective platforms for drug delivery, immunomodulation, and phototherapy. In this review, we mainly discuss the recent application of CDs in tumor immunotherapy and the prospects of CDs in the field of immune medicine. By assessing the achievements and challenges of CDs in tumor immunotherapy, our review would provide mechanistic insights into the evolution of future nanomedicine.