Argonaute (AGO) proteins play important roles in RNA silencing processes through formation of complexes with the mature microRNAs. In this study, a wheat AGO gene referred to TaAGO1, which shares high similarities to AtAGO1 in Arabidopsis and OsAGO1 in rice, was characterized. As a cDNA full length of 3747 bp, TaAGO1 encodes a 1099-aa polypeptide with a molecular weight of 122 kD and an isoelectric point (pI) of 9.52. Subcellular prediction analysis suggests that TaAGO1 is to target onto the cytoplasm after endoplasmic reticulum (ER) sorted. Similar to AtAGO1 and OsAGO1, TaAGO1 contains PIWI and DDH, two conserved domains in AGOs. Phylogenetic analysis indicated that TaAGO1 was possibly derived from different progenitors with its homologous across diverse plant species. The transcripts of TaAGO1 were significantly regulated by the stresses of phosphorus deprivation and dehydration, and exogenous treatment of abscisic acid (ABA), suggesting that this wheat AGO member also exerts roles on mediating above signaling transductions. Southern blotting analysis revealed that genome AA, SS, and DD, three diploids composing of the hexaploid wheat, all harbored two copies of TaAGO1. Down-regulation of TaAGO1 in wheat led to conspicuously phenotypic alterations of the young plantlets, with a variety of abnormal growth features. Taking the results in this study together, it was implicated that TaAGO1 exists as a subset of copies in wheat and plays critical roles on silencing of appropriate target genes via regulation of TaAGO1-MiRNAs complex formation.