Arabidopsis SUPERMAN (SUP) and its family members have been implicated in flower organogenesis and plant morphogenesis via the regulation of division or growth of cells. In this study, we characterized a new SUP-like zinc finger gene (AtZFP12). This gene is expressed around the bases of the axillary buds and at the junction between the inflorescence axis and flower stalks. It is also expressed at the boundary between the meristematic and elongation zones in root tips. Overexpression of its cDNA in transgenic Arabidopsis reduced cell expansion, resulting in dwarfed plant growth. These results suggest the potential role of AtZFP12 in the regulation of cell growth during the establishment of SOB in the shoot and transition zones in root tips.