Alkyl 2-cyano-3-methylthio-3-phosphonylacrylates were synthesized by the reaction of alkyl 2-cyano-3,3-dimethylthioacrylates with dialkyl phosphites. The structures of the new compounds were characterized by elemental analyses, IR, 1H-, 13C- and 31P-NMR spectral data. These compounds were tested in vitro against pathogenic fungi, namely, Fusarium graminearum, Cytospora mandshurica and Fusarium oxysporum. Amongst all compounds, 2d and 2t were found to be effective against the tested fungi at 50 microg/mL. A half-leaf method was used to determine the in vivo protective, inactivation and curative efficacies of the title products against tobacco mosaic virus (TMV). Title compounds 2a and 2b were found to possess good in vivo curative, protection and inactivation effects against TMV with inhibitory rates at 500 mg/L of 60.0, 89.4 and 56.5 and 64.2, 84.2 and 61.2 %, respectively. To the best of our knowledge, this is the first report on the antiviral and antifungal activity of alkyl 2-cyano-3-methylthio-3-phosphonylacrylates.