Dehydroabietic acid R=COOH (DHA), a naturally occuring diterpene resin acid, is an activator of systemic acquired resistance (SAR) under biotic stress. However, there had been no report on its functioning under salinity. In the present study, we determined the effects of DHA on salinity and its possible role as a signal transmitter in soybean (Glycine max L.) leaves under salinity (200 mM NaCl). Furthermore, physiological parameters, chlorophyll, proline, malondialdehyde (MDA), hydrogen peroxide (H2O2) content, superoxide (O2‾) and hydroxyl radical (•OH) scavenge capacity, as well as antioxidant enzymes (SOD, POX, APX and GST) and GmWRKY-71 gene expressions were investigated in the treated plants at 6 h, 12 h and 24 h. The obtained results showed that pretreatment of DHA caused (1) a reduction in salt-induced damage, (2) improvement in biomass yield, water status, chlorophyll and leaf area, (3) regulation of the proline level and relative electrolyte leakage, (4) increase in reactive oxygen species (ROS) scavenging capacity, (5) induction of SOD and APX enzyme activity at all the investigated periods, while POX only at 6 h, and thus alleviation of the oxidative damage. In addition, the changes in GmWRKY-71 gene expressions were remarkable in soybean under salinity. To sum up, these results showed that DHA can be used as a ROS inhibitor or a signal molecule in increasing salt tolerance in soybean under salinity.