Methylated soy and chickpea proteins (MSP and MCP, respectively), and 11S globulin (a soy protein fraction), are characterized by net positive charges and a more hydrophobic nature, nominating them as antiviral proteins. Under greenhouse conditions, potato plants (cv. Spunta) mechanically infected with potato virus Y (PVY) and potato virus X (PVX) were treated with MSP, MCP, and 11S globulin at diferent concentrations, after ten days of infection. The three tested substances inhibited the viral propagation, where the concentration 500 µg ml−1 produced the maximum antiviral action. This infuence was further augmented by applying the material twice 10 and 20 days after the viral infection. Assessing the viral load by a double antibody sandwich ELISA (DAS-ELISA), dot-blot hybridization, and reverse transcription-polymerase chain reaction (RT-PCR) confrmed the viral inhibition, in the following order: MSP>MCP>11S globulin. Bringing the virus in contact with MCP produced deformed TEM (transmission electron microscope) viral micrographs referring to a potential direct action of the substance on the virus. The tested materials’ antiviral activity at 500 µg ml−1 was positively refected on the growth and yield of PVY or PVX-infected potato plants cultivated under open feld conditions in January. Considerably high increases in the tuber yield of either PVY-infected (68, 42, and 36%) or PVX-infected plants (52, 41 and 30%), were produced by the treatment with MSP, MCP and 11S (500 µg ml−1), respectively