Peptide vaccines are an attractive new tool for cancer therapy. Delivery of tumor antigenic peptides to dendritic cells can stimulate potent tumor-specific T cells. Work over the last decade has shown that particulate vaccines activate more T cells in vitro than soluble protein, and that peptides targeted to dendritic cells are more effective immune stimulants than untargeted peptides in vivo. We describe a new nanostructured, modular peptide vaccine particle that provides exquisite control over composition to a degree unseen in current particles. Our architecture combines the benefits of a high antigen dose and dendritic cell targeting with the capability to easily add new functionalities. We describe the construction of the vaccine particles and, using ovalbumin as a model antigen, demonstrate their effectiveness in an in vitro system.