MicroRNA167 (miR167), as a conserved miRNA, has been implicated in auxin signalling by regulating the expression of certain auxin response factor (ARF) genes to determine the plant developmental process. Among the 10 MIR167 genes of rice, the precursor structures derived from MIR167a, MIR167b and MIR167c produce miR167 with high efficiency. To explore the biological function of miR167 in rice, four of its predicted target genes, OsARF6, OsARF12, OsARF17 and OsARF25, were identified in vivo. Although the expression levels of miR167 and its target OsARFs did not show an obvious negative correlation, the enhanced miR167 level in transgenic rice overexpressing miR167 resulted in a substantial decrease in mRNA levels of the four OsARF genes. Moreover, the transgenic rice plants were small in stature with remarkably reduced tiller number. These results suggest that miR167 is important for the appropriate expression of at least four OsARFs, which mediate the auxin response, to contribute to the normal growth and development of rice.