The emphasis on viruses as disease-causing agents has skewed scientists’ perception of other aspects of viruses. In recent years, there has been a re-orientation of virus studies toward the beneficial use of viruses, independent of their disease-causing phenotypes. For example, plant viral capsids have been utilized as biotemplates, drug vectors and nanodevices in many practical applications. By studying the morphology, genetics, spatial folding, replication and assembly strategy of viral capsids, we can manipulate the viral genome and viral proteins for in various fields. At present one of the most important uses of plant viruses is in nanomedicine, where they can be employed in diagnosis and therapy. Their low toxicity for humans and their specific effects are the main advantages of using plant viral nanoparticles. This review discusses applications of plant viruses in bionanotechnology.