Immunization using vaccine has been very successful in combating infectious diseases for more than 200 years now. With understanding of immunology and advancements in molecular biology, it has been possible to develop newer and more efficacious vaccines. However, the new generation vaccines lack the adjuvant and immunostimulatory properties of live/attenuated vaccines. In such scenario, nanotechnology based formulations offer numerous advantages for vaccine developments. Nanocarriers such as liposomes, polymeric particles, virosomes, lipid nanoparticles etc. help in improving the immunogenicity of new generation vaccines. These nanocarrier systems protect the vaccines from degradation, improves its stability, provide adjuvant effect and help in targeting of the antigen to the antigen presenting cells (APCs). It is possible to elicit innate, humoral, cellular or mucosal immune response from antigen formulated with nanocarrier systems. These nanoparticle based systems also offer the advantages of administration in various possible routes. Among the nanocarrier systems, polymer particles have been most widely explored for vaccine developments. Notable among them are particles made from biodegradable polymers of synthetic and natural origin. These polymeric nanoparticles offer numerous advantages for vaccine developments. Formulation of single dose vaccine, elicitation of T cell response, modulation of immune response and mucosal immunity are a few applications of nanotechnology based vaccine formulation. Activation of dendritic cells, vaccination against allergy, tumor immunotherapy and use of polymer particles as an artificial APCs open new possibilities in controlling infection, cancer and other complex diseases.