Porcine reproductive and respiratory syndrome (PRRS) has caused huge economic losses in the swine industry worldwide. Live and inactivated vaccines have only been partially successful in generating protective immune responses. The PRRS virus (PRRSV) glycoprotein 5 (GP5) is a major viral antigenic target and is thus suitable for development of genetically engineered PRRSV vaccines. Here, a modified GP5 and ferritin were fused and expressed using a baculovirus system to generate a GP5m-ferritin nanoparticle vaccine. We demonstrated that the GP5m-ferritin vaccine elicited higher serum antibody titers in pigs than inactivated PRRSV. Moreover, immunization with GP5m-Ft promoted a Th1-dominant cellular immune response and enhanced specific T-lymphocyte immune responses. GP5m-ferritin-vaccinated pigs had significantly lower mean rectal temperatures, respiratory scores, viremia, and macroscopic and microscopic lung lesion scores post-challenge compared with unvaccinated pigs. These results indicated that GP5m-ferritin subunit vaccines can elicit specific protective immune responses and represent promising vaccine candidates.