Complex antagonistic interactions between abscisic acid (ABA) and brassinosteroid (BR) signaling pathways have been widely documented. However, whether or how ABA interacts synergistically with BR in plants remains to be elucidated. Here we report that low but not high concentration of ABA increases lamina joint inclination of rice seedling, which requires functional BR biosynthesis and signaling. Transcriptome analyses confirm that about 60% of low concentration ABA early response genes can be regulated by BR in the same directions. ABA activates BR signal in a fast, limited, and short-term manner, and the BR biosynthesis regulatory gene, OsGSR1, plays a key role during this process, whose expression is induced slightly by ABA through transcriptional factor ABI3. Moreover, the early short-term BR signal activation is also important for ABA-mediated salt stress tolerance. Intriguingly, the process and effect of short-term BR signal activation were covered by high concentration of ABA, implying adaptive mechanisms existed in plant to cope with varying degrees of stress.