Cancer is one of the major diseases threatening global public health. The high incidence, high mortality rate, and easy metastasis and recurrence of cancer pose severe challenges to clinical treatment. Traditional therapies, including surgery, radiotherapy, chemotherapy, and cancer vaccines, can alleviate the condition of cancer and stimulate specific immune responses in the body. Unfortunately, traditional therapies still have limitations, such as poor specificity, strong toxicity and side effects, and easy induction of drug resistance. Hydrogel vaccines (HVs), as an innovative technology in the field of cancer immunotherapy, have attracted extensive attention due to their remarkable biocompatibility, biodegradability, and drug release properties. In-depth exploration of the functional characteristics of HVs and their application in cancer immunotherapy holds significant guiding importance for the design of HVs with specific functionalities. Hence, this review summarizes the materials, preparation methods, and properties of HVs. Moreover, this review focuses on elaborating the action mechanisms and application progress of HVs in cancer immunotherapy. Finally, this review looks forward to the future development direction and clinical transformation prospects of HVs. The findings provide feasible solutions for tumor treatment.