BACKGROUND: Sepsis is a life-threatening disease caused by infection, and developing novel strategies against sepsis is still required. Exosomes derived from mesenchymal stem cells (MSCs) have shown promising therapeutic potential for various diseases. In this study, we aimed to investigate the action and mechanism of exosomes derived from IL-1β-pre-conditioned bone marrow-derived mesenchymal stromal cells (BMSCs) in sepsis. METHODS: Exosomes were isolated from BMSCs that were pretreated with (IL-1β- BMSC/exos) or without IL-1β (BMSC/exos). RESULTS: IL-1β-BMSC/exos significantly enhanced the proliferation, migration, and tube formation of HUVECs. Treatment with LPS induced the expression of high mobility group box 1 (HMGB1) and the phosphorylation of AKT in HUVECs, but these effects were counteracted by the treatment of IL-1β-BMSC/exos. The protective effect of IL-1β-BMSC/exos on the viability and tube formation ability of HUVECs was reversed by overexpression of HMGB1. Moreover, IL-1β-BMSC/exos promoted the polarization of M2 macrophages and reduced the secretion of inflammatory chemokines. Additionally, IL-1β-BMSC/exos alleviated cecal ligation and puncture (CLP)-induced sepsis CONCLUSION: IL-1β-BMSC/exos alleviates sepsis by modulating the HMGB1/AKT pathway and triggering M2 macrophage polarization.