This review discusses ABA-mediated transcriptional regulation in response to osmotic stress in Arabidopsis. ABA is a key plant hormone involved in various developmental processes and stress responses. During seed maturation and vegetative growth, cellular dehydration increases endogenous ABA levels, which regulate many dehydration-responsive genes. In Arabidopsis, ABA regulates nearly 10% of protein-coding genes, a higher percentage than other plant hormones. Gene expression is mainly regulated by two families of bZIP transcription factors, ABI5 in seeds and AREB/ABFs in vegetative tissues, in an ABA-responsive element (ABRE)-dependent manner. The SnRK2-AREB/ABF pathway governs most ABA-mediated ABRE-dependent gene expression during vegetative growth in response to osmotic stress. Other factors, such as the circadian clock and light conditions, also regulate ABA-mediated gene expression, contributing to stress tolerance and growth repression. Various other transcription factors, including AP2/ERF, MYB, NAC, and HD-ZF, have been reported to participate in ABA-mediated gene expression. ABA-mediated gene expression appears to confer versatile tolerance and repress growth under osmotic stress conditions in a circadian-dependent manner. Increased ABA levels in response to osmotic stress induce the expression of many genes involved in dehydration response and tolerance. ABA-induced genes include those encoding proteins associated with stress response and tolerance, regulatory proteins, transporters, and enzymes involved in osmoprotectant synthesis. Conversely, genes down-regulated by ABA are enriched for those encoding proteins involved in growth and development. The integration of transcriptome and metabolome data sets has revealed that drought-induced ABA-dependent transcriptional regulation plays a pivotal role in carbohydrate metabolism and in the biosynthesis of branched-chain amino acids, saccharopine, proline, and polyamine. Nearly 10% of the protein-coding genes in Arabidopsis are likely to be regulated by ABA. These findings suggest that ABA-mediated gene expression plays a versatile and pivotal role in plants. The ABRE is the major cis-element in ABA-induced gene expression. Most ABA-regulated genes contain conserved ABREs as the determinant cis-elements in their promoters. ABREs contain an ACGT core, which has been recognized by plant bZIP proteins. A single copy of ABRE is not sufficient to confer ABA-mediated induction of transcription. Successful ABA-induced gene expression requires either additional copies of the ABRE or coupling elements. The other regulatory elements associated with ABA-induced gene expression will be discussed below in the section corresponding to each TF.This review discusses ABA-mediated transcriptional regulation in response to osmotic stress in Arabidopsis. ABA is a key plant hormone involved in various developmental processes and stress responses. During seed maturation and vegetative growth, cellular dehydration increases endogenous ABA levels, which regulate many dehydration-responsive genes. In Arabidopsis, ABA regulates nearly 10% of protein-coding genes, a higher percentage than other plant hormones. Gene expression is mainly regulated by two families of bZIP transcription factors, ABI5 in seeds and AREB/ABFs in vegetative tissues, in an ABA-responsive element (ABRE)-dependent manner. The SnRK2-AREB/ABF pathway governs most ABA-mediated ABRE-dependent gene expression during vegetative growth in response to osmotic stress. Other factors, such as the circadian clock and light conditions, also regulate ABA-mediated gene expression, contributing to stress tolerance and growth repression. Various other transcription factors, including AP2/ERF, MYB, NAC, and HD-ZF, have been reported to participate in ABA-mediated gene expression. ABA-mediated gene expression appears to confer versatile tolerance and repress growth under osmotic stress conditions in a circadian-dependent manner. Increased ABA levels in response to osmotic stress induce the expression of many genes involved in dehydration response and tolerance. ABA-induced genes include those encoding proteins associated with stress response and tolerance, regulatory proteins, transporters, and enzymes involved in osmoprotectant synthesis. Conversely, genes down-regulated by ABA are enriched for those encoding proteins involved in growth and development. The integration of transcriptome and metabolome data sets has revealed that drought-induced ABA-dependent transcriptional regulation plays a pivotal role in carbohydrate metabolism and in the biosynthesis of branched-chain amino acids, saccharopine, proline, and polyamine. Nearly 10% of the protein-coding genes in Arabidopsis are likely to be regulated by ABA. These findings suggest that ABA-mediated gene expression plays a versatile and pivotal role in plants. The ABRE is the major cis-element in ABA-induced gene expression. Most ABA-regulated genes contain conserved ABREs as the determinant cis-elements in their promoters. ABREs contain an ACGT core, which has been recognized by plant bZIP proteins. A single copy of ABRE is not sufficient to confer ABA-mediated induction of transcription. Successful ABA-induced gene expression requires either additional copies of the ABRE or coupling elements. The other regulatory elements associated with ABA-induced gene expression will be discussed below in the section corresponding to each TF.