The mechanism of the protective effect of quercetin-3-O-${eta}$-D-glucuronopyranoside (QGC) from the leaves of Rumex aqauticus on indomethacin (IND, a representative NSAID)-induced gastric damage in rats was investigated. Pre-treatment with QGC significantly attenuated IND-induced gastric mucosal injury. An increase in myeloperoxidase (MPO) activity and expression of intercellular adhesion molecule (ICAM)-1 protein and mRNA expression of the pro-inflammatory cytokines tumor necrosis factor-${alpha}$ and interleukin-$1{eta}$, as well as a decrease in gastric mucus secretion were detected in the gastric mucosa of IND-treated rats. QGC reversed the side effect of IND on MPO activity and mucus production. Furthermore, QGC pre-treatment notably decreased ICAM-1 protein and mRNA expression of the pro-inflammatory cytokines, suggesting that QGC protection from IND-induced damage is associated with increased gastric mucus secretion, inhibition of free radical production by activated neutrophils via ICAM-1, and pro-inflammatory cytokine downregulation.