Objective To investigate the effects of nicotinamide phosphoribosyl transferase (NAMPT) inhibitor FK866 on polymicrobial sepsis-induced liver injury in mice. Methods Eighty-four healthy male C57BL/6J mice were divided into four groups by random number table method (n = 21): sham group, sepsis-induced liver injury model by cecal ligation and perforation group (CLP group), vehicle+CLP group and FK866+CLP group. FK866 (10 mg/kg) or same volume dimethyl sulfoxide were given intraperitoneally into mice 24, 12 and 0.5 hours prior to CLP in the FK866+CLP group or the vehicle+CLP group, respectively. Fifteen mice in each group were used to observe the 48-hour survival after operation. The remaining 6 mice were sacrificed 20 hours after operation to harvest venous blood and liver tissue samples for index detection. The levels of serum alanine transaminase (ALT) and aspartate aminotransferase (AST) were measured by colorimetry; the levels of serum NAMPT, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were measured by enzyme linked immunosorbent assay (ELISA); the mRNA expressions of TNF-α and IL-6 were measured by real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR); the protein expressions of hepatic NAMPT, cytoplasmic IκBα and nuclear factor-κB (NF-κB) were measured by Western Blot. Results Compared with the sham group, the 48-hour survival in the CLP group was significantly decreased; serum and liver NAMPT protein levels were significantly increased, serum ALT, AST, TNF-α, IL-6 levels and mRNA expressions of TNF-α, IL-6 in liver tissue were significantly increased; the expression of cytoplasmic IκBα protein was significantly decreased, and the expression of nuclear NF-κB protein was significantly increased; which indicated that CLP induced NF-κB activation, inflammation and liver injury. There was no significant difference between the vehicle+CLP group and the CLP group. Compared with the vehicle+CLP group, the 48-hour survival in FK866+CLP group was significantly increased (53.33% vs. 26.67%); serum ALT, AST, TNF-α, IL-6 levels and mRNA expressions of TNF-α, IL-6 in liver tissue were significantly decreased [serum ALT (U/L): 128.94±32.48 vs. 237.24±58.61, serum AST (U/L):289.89±68.74 vs.468±82.17, serum TNF-α (pg/L): 65.17±18.74 vs.127.64±48.18, serum IL-6 (ng/L): 31.78±5.23 vs. 60.87±13.12, liver TNF-α mRNA (2-ΔΔCt): 8.37±4.17 vs. 18.24±6.12, liver IL-6 mRNA (2-ΔΔCt): 18.58±7.12 vs.34.24±6.71], the expression of cytoplasmic IκBα protein was significantly increased (IκBα/GAPDH: 0.23±0.03 vs. 0.12±0.04), while expression of nuclear NF-κB protein was significantly decreased (NF-κB/Lamin B1: 0.25±0.04 vs. 0.42±0.05), with statistically significant differences (all P < 0.05). Conclusion NAMPT inhibitor FK866 protects polymicrobial sepsis-induced liver injury via the inhibition of NF-κB activation and inflammation.