Di19 (drought-induced protein19) family is a novel type of Cys2/His2 zinc-finger proteins. In this study, Arabidopsis Di19-3 was functionally characterized. The experimental results revealed that AtDi19-3 is a transcriptional activator, and could bind to the TACA(A/G)T sequence. AtDi19-3 expression in plants was remarkably induced by NaCl, mannitol and abscisic acid (ABA). T-DNA insertion mutation of AtDi19-3 results in an increase in plant tolerance to drought and high salinity stresses and ABA, whereas overexpression of AtDi19-3 leads to a drought-, salt- and ABA-sensitive phenotype of the transgenic plants. In the presence of NaCl, mannitol or ABA, rates of seed germination and cotyledon greening in Atdi19-3 mutant were higher, but in AtDi19-3 overexpression transgenic plants were lower than those in wild type. Roots of Atdi19-3 mutant seedlings were longer, but those of AtDi19-3 overexpression transgenic seedlings were shorter than those of wild type. Chlorophyll and proline contents in Atdi19-3 mutant were higher, but in AtDi19-3 overexpression seedlings were lower than those in wild type. Atdi19-3 mutant showed greater drought-tolerance, whereas AtDi19-3 overexpression transgenic plants exhibited more drought-sensitivity than wild type. Furthermore, expression of the genes related to ABA signaling pathway was altered in Atdi19-3 mutant and AtDi19-3 transgenic plants. These data suggest that AtDi19-3 may participate in plant response to drought and salt stresses in an ABA-dependent manner.