An important property of some spherical plant viruses is their ability to reassemble in vitro from native capsid protein (CP) and RNA into infectious virus-like particles (VLPs). Virions of cucumber mosaic virus (CMV) are stabilized by protein-RNA interactions and the nucleic acid is essential for assembly. This study demonstrated that VLPs will form in the presence of both ssDNA and dsDNA oligonucleotides, and with a lower size limit of 20 nt. Based on urea disruption assays, assembled VLPs from CMV CP and RNA (termed ReCMV) exhibited a level of stability similar to that of virions purified from plants, whilst VLPs from CMV CP and a 20mer exhibited comparable or greater stability. Fluorescent labelling of VLPs was achieved by the encapsidation of an Alexa Fluor 488-labelled 45mer oligonucleotide (ReCMV-Alexa488-45) and confirmed by transmission electron and confocal microscopy. Using ssDNA as a nucleating factor, encapsidation of fluorescently labelled streptavidin (53 kDa) conjugated to a biotinylated oligonucleotide was observed. The biological activity and stability of ReCMV and ReCMV-Alexa488-45 was confirmed in infectivity assays and insect vector feeding assays. This work demonstrates the utility of CMV CP as a protein cage for use in the growing repertoire of nanotechnological applications.