SummaryHigh‐salinity stress affects plant growth and development. We have previously reported that overexpression of the salinity‐responsive DWARF AND DELAYED FLOWERING 1 (DDF1) gene, encoding an AP2 transcription factor of the DREB1/CBF subfamily, causes dwarfism mainly by levels of reducing bioactive gibberellin (GA) in transgenic Arabidopsis. Here, we found that the GA 2‐oxidase 7 gene (GA2ox7), which encodes a C20‐GA deactivation enzyme, is strongly upregulated in DDF1‐overexpressing transgenic plants. A loss‐of‐function mutation of GA2ox7 (ga2ox7‐2) suppressed the dwarf phenotype of DDF1‐overexpressing plants, indicating that their GA deficiency is due to overexpression of GA2ox7. Transient overexpression of DDF1 activated the promoter of GA2ox7 in Arabidopsis leaves. A gel shift assay showed that DDF1 binds DRE‐like motifs (GCCGAC and ATCGAC) in the GA2ox7 promoter. In Arabidopsis under high‐salinity stress, six GA2ox genes, including GA2ox7, were upregulated. Furthermore, the ga2ox7‐2 mutant was less growth retarded than wild‐type Col under high‐salinity stress. These results demonstrate that, under salinity stress, Arabidopsis plants actively reduce endogenous GA levels via the induction of GA 2‐oxidase, with the result that growth is repressed for stress adaptation.