Multifunctional nanoparticles hold promise as the next generation of therapeutic delivery and imaging agents. Nanoparticles comprising many types of materials are being tested for this purpose, including plant viral capsids. It has been found that Red clover necrotic mosaic virus (RCNMV) can be loaded with significant amounts of therapeutic molecules with molecular weights of 600 or even greater. Formulation of RCNMV into a plant viral nanoparticle (PVN) involves the loading of cargo and attachment of peptides. In this study, we show that targeting peptides (less than 16 amino acids) can be conjugated to the capsid using the heterobifunctional chemical linker sulfosuccinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate (Sulfo-SMCC). The uptake of both native RCNMV capsids and peptide-conjugated RCNMV was tested in the HeLa cell line for peptides with and without fluorescent labels. Uptake of RCNMV conjugate with a CD46 targeting peptide was monitored by flow cytometry. When formulated PVNs loaded with doxorubicin and armed with a targeting peptide were delivered to HeLa cells, a cytotoxic effect was observed. The ability to modify RCNMV for specific cell targeting and cargo delivery offers a method for the intracellular delivery of reagents for research assays as well as diagnostic and therapeutic applications.