The development of vaccines and the rise of the modern vaccinology are considered iconic global milestones in the history of human and veterinary medicine. The consistent use of vaccines is clearly the most cost-effective strategy both at the individual patient level as well as a public health policy. Nonetheless, we still lack vaccine solutions for many important infectious diseases and cancers. Reasons for particular failures reside mostly in the fact that classical vaccine strategies have been incapable to deliver satisfactory levels of immunogenicity and/or safety. In these cases, the development of alternative vaccine approaches appears as possible solutions to be evaluated. One such alternative strategy is the use of functionalized carbon nanotubes (f-CNT) as antigen carriers in vaccine formulations. Advantages of this kind of nanocomposite include the fact that f-CNTs are able to penetrate cells and deliver proteins within the cytoplasm, where they associate to both types of main histocompatibility complex molecules generating broad immune responses. Moreover, f-CNTs are able to modulate the immune response and function as adjuvants. There are many other important properties that make f-CNTs interesting for vaccine design, and possible drawbacks that need to be overcome before these nanocompoites can be effectively turned into usable vaccines.