Although nanomaterials (NMs) may inhibit viral pathogens, the mechanisms governing plant–virus–nanomaterial interactions remain unknown. Nicotiana benthamiana plants were treated with nanoscale titanium dioxide (TiO2) and silver (Ag), C60 fullerenes, and carbon nanotubes (CNTs) at 100, 200 and 500 mg L−1 for a 21-day foliar exposure before inoculation with GFP-tagged tobacco mosaic virus (TMV). Plants treated with CNTs and C60 (200 mg L−1) exhibited normal phenotype and viral symptomology was not evident at 5 days post-infection. TiO2 and Ag failed to suppress viral infection. RT-qPCR analysis revealed that viral coat protein transcript abundance and GFP mRNA expression were reduced 74–81% upon CNTs and C60 treatment. TEM revealed that the chloroplast ultrastructure in carbon NM-treated plants was unaffected by TMV infection. Fluorescence measurement of CNTs and C60 (200 mg L−1) treated plants indicated photosynthesis equivalent to healthy controls. CNTs and C60 induced upregulation of the defense-related phytohormones abscisic acid and salicylic acid by 33–52%; the transcription of genes responsible for phytohormone biosynthesis was elevated by 94–104% in treated plants. Our findings demonstrate the protective role of carbon-based NMs, with suppression of TMV symptoms via hindered physical movement and viral replication. Given the lack of viral phytopathogen treatment options, this work represents a novel area of nano-enabled agriculture. Display omitted •Current study reveals the mechanisms governing plant–virus–nanomaterial interactions.•Carbon-based NMs play a protective role against single-stranded RNA TMV.•Early foliar exposure of carbon-based NMs at 200 mg L−1 inhibits TMV replication and systemic infection of apical tissues.•NMs augment the plant’s immunity by improving photosynthetic performance and triggering defense responses against TMV.