Objective: Numerous studies have shown that bone marrow-derived mesenchymal stem cells (MSCs) enhance neurological recovery after cerebral ischemia. However, the mechanisms are still not clear. The present study aimed to investigate the beneficial effects of MSCs on global cerebral ischemia induced by cardiac arrest (CA) and the underlying mechanisms. Methods: Rats subjected to asphyxial CA were injected intravenously with MSCs (5×106) at 2 hours after resuscitation. Whole brain histopathologic damage scores (HDS) were assessed by histopathology at 3 and 7 days after resuscitation. The distribution of donor MSCs in the brain was evaluated. The expression of tumor necrosis factor-α-induced protein 6 (TSG-6) and pro-inflammatory cytokines in cerebral cortex was assayed. After intravenous infusion of TSG-6 siRNA-MSCs, HDS and pro-inflammatory cytokines were reevaluated at 7 days after resuscitation. Results: Intravenously administered MSCs significantly reduced whole brain HDS after global cerebral ischemia. Immunofluorescence microscopy revealed that donor MSCs were primarily found in cerebral cortex and expressed TSG-6. MSCs treatment significantly increased the expression of TSG-6 and reduced the expression of pro-inflammatory cytokines in cerebral cortex. In addition, intravenous infusion of TSG-6 siRNA-MSCs failed to attenuate brain inflammation. Conclusion: Systemically administered MSCs reduced inflammatory damage to brain in rats with global cerebral ischemia via secretion of TSG-6. © 2016, ASEAN Neurological Association. All Rights Reserved.