ABSTRACT: Objective: Significant progress has been made in critical care medicine during the past several decades. However, the mortality rate is still high in patients with sepsis, especially with acute kidney injury (AKI). Mesenchymal stem cells (MSCs) possess an ability to ameliorate renal injury from ischemia-reperfusion, but it is still unknown whether they have the ability to reduce sepsis-associated AKI. Methods: Male C57BL/6 mice underwent cecal ligation and puncture operation to induce sepsis and then received either normal saline or MSCs (1 × 106 cells intravenously) 3 h after surgery. Results: Within 24 h after cecal ligation and puncture operation, the septic mice developed kidney injury and exhibited a higher mortality. Treatment with MSCs decreased serum creatinine and blood urea nitrogen levels and improved recovery of tubular function. mRNA levels of interleukin 6 (IL-6), IL-17, tumor necrosis factor α, interferon γ, CXCL1, CXCL2, CXCL5, CCL2, and CCL3 in kidney tissue were dramatically decreased after MSC treatment. Neutrophil infiltration in kidney and blood bacterial loads were attenuated after MSC injection. Moreover, mice treated with MSCs had a higher survival rate than the saline treatment group. Injected MSCs were mainly localized in the lungs, spleen, and abdominal cavity lymph node, but not in the kidneys. Conclusions: Treatment with MSCs can alleviate sepsis-associated AKI and improve survival in mice with polymicrobial sepsis. These effects may be mediated by the inhibition of IL-17 secretion and balance of the proinflammatory and anti-inflammatory states. Mesenchymal stem cells may be a potential new therapeutic agent for the prevention or reduction of sepsis-associated AKI.