Highly conserved mitogen-activated protein kinase (MAPK) cascades regulate numerous plant processes, including hormonal responses, stress, and innate immunity. In this research,TaMAPK4was predicted to be a target of tae-miR164. We verified the binding and suppression ofTaMAPK4by co-expression inNicotiana benthamiana. Moreover, we foundTaMAPK4was localized in the cytoplasm and nucleus using transient expression analyses.TaMAPK4transcripts increased following salicylic acid (SA) treatment and when host plants were infected with an avirulent race of the stripe-rust pathogen. Silencing ofTaMAPK4by virus-induced gene silencing permitted increased colonization by the avirulent pathogen race. Detailed histological results showed increasedPuccinia striiformis(Pst) hyphal length, hyphal branches, and infection uredinial size compared to the non-silenced control. SA accumulation and the transcript levels ofTaPR1, TaPR2, andTaPR5were significantly down-regulated inTaMAPK4knockdown plants. Overall, these results suggest thatTaMAPK4plays an important role in signaling during the wheat-Pstinteraction. These results present new insights into MAPK signaling in wheat defense to rust pathogen.