Adverse gastrointestinal (GI) effects caused by nonsteroidal anti-inflammatory drugs (NSAIDs), including indomethacin, are recognized as the major limitation to their clinical use. NSAID-induced gastric damage is generated by cyclooxygenase inhibition, activation of inflammatory processes, and oxidative stress. Docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid, has shown gastroprotective effects; however, the molecular mechanisms underlying these effects have not been fully explained. As a result, the aim of this study was to examine DHA's anti-inflammatory and antioxidative actions in a mouse model of indomethacin-induced gastric injury. Oral administration of DHA (3, 10, 30, and 100 mg/kg) caused a reduction in indomethacin-induced gastric hemorrhagic lesions. We found that the gastroprotective effects of DHA treatment (100 mg/kg) were accompanied by decreases in several parameters: in leukocyte recruitment; gastric levels of myeloperoxidase; leukotriene B4; intercellular adhesion molecule-1; tumor necrosis factor alpha; and nuclear translocation of nuclear factor-κB. Concurrently, we observed an improvement in antioxidant defenses produced by the increase in superoxide dismutase and glutathione activities but not catalase; in addition, a decrease in some oxidative damage markers such as malondialdehyde and carbonyl proteins in lipids and proteins was observed. Furthermore, resolvin D1 production and expression of free fatty acid receptor 4 were stimulated by DHA. Therefore, this study identified the antioxidant and anti-inflammatory actions of DHA as the main mechanisms involved in DHA's gastroprotective effects against indomethacin-induced gastric damage.