Coordinated regulation of the many genes controlling leaf, flower, and root development determines the phenotypes of plants; this regulation requires exquisite control of many transcription factors, including the WUSCHEL-related homeobox (WOX) family. We recently reported that rice (Oryza sativa) WUSCHEL-related homeobox 3A (OsWOX3A) plays important roles in organ development, including lateral-axis outgrowth and vasculature patterning in leaves, lemma and palea morphogenesis in spikelets, and the numbers of tillers and lateral roots. OsWOX3A is encoded by NARROW LEAF2 (NAL2) and NAL3, a pair of duplicated genes. In this study, further analysis of nal2 nal3 (hereafter nal2/3) double mutants revealed that, in addition to its role in lateral root development, OsWOX3A also acts in the control of root hair formation. Based on this new finding, we describe a possible mechanism by which OsWOX3A regulation of auxin transport genes acts in root development.