Plant basic-leucine zipper (bZIP) transcription factors play important roles in many biological processes and are involved in the regulation of salt stress tolerance. Previously, our lab generated digital gene expression profiling (DGEP) data to identify differentially expressed genes in a salt-tolerant genotype of Glycine soja (STGoGS) and a salt-sensitive genotype of Glycine max (SSGoGM). This DGEP data revealed that the expression (log2 ratio) of GmbZIP110 was up-regulated 2.76-fold and 3.38-fold in SSGoGM and STGoGS, respectively. In the present study, the salt inducible gene GmbZIP110 was cloned and characterized through phylogenetic analysis, subcellular localization and in silico transcript abundance analysis in different tissues. The functional role of this gene in salt tolerance was studied through transactivation analysis, DNA binding ability, expression in soybean composite seedlings and transgenic Arabidopsis, and the effect of GmbZIP110 on the expression of stress-related genes in transgenic Arabidopsis was investigated. We found that GmbZIP110 could bind to the ACGT motif, impact the expression of many stress-related genes and the accumulation of proline, Na(+) and K(+), and enhanced the salt tolerance of composite seedlings and transgenic Arabidopsis. Integrating all these results, we propose that GmbZIP110 plays a critical role in the response to salinity stress in soybean and has high potential usefulness in crop improvement.