Approaches capable of simultaneously treating cancer and protecting susceptible patients from lethal infections such as coronavirus disease 2019, are highly desirable but prove to be difficult. Here, dressing bacteria with a hybrid immunoactive nanosurface is reported to elicit dual anticancer and antiviral immunity. A combination of a checkpoint blocking antibody and a virus‐specific antigen is covalently conjugated to polydopamine nanoparticles, which can be anchored onto bacterial surface, by a one‐step in situ polymerization of dopamine under a cell‐friendly condition. By virtue of the ability to colonize and penetrate deep tumor tissue, dressed bacteria enable sustained release and expanded exposure of carried immunoactivators to stimulate immune cells. In addition to a carrier role, bacteria are able to further provoke innate immunity due to the native immunogenicity of the pathogen‐associated molecular patterns. Immunization with dressed bacteria promotes the maturation, and activation of antigen‐presenting cells, which induces robust humoral and cellular immune responses in tumor‐bearing mice. As evidenced by efficient production of viral‐antigen‐specific immunoglobulin G antibody in serum and significantly suppressed tumor growth in different models, dressing bacteria with a hybrid immunoactive nanosurface paves an avenue to prepare next‐generation therapeutics for synergistic treatment and prevention.