Myocardial cell injury or cardiomyopathy is associated with excessive inflammatory response and apoptosis of cardiac myocytes during sepsis. MicroRNA-23b (miR-23b) is a multifunctional miRNA that is considered to regulate immunosuppression in sepsis. The aim of this study was to examine the effect of miR-23b on cardiomyopathy induced by sepsis and to explore the potential mechanism involved. Sprague-Dawley rats were subjected to cecal ligation and puncture (CLP), and the level of miR-23b at different time points was measured by quantitative real-time polymerase chain reaction (qPCR). Then, we overexpressed miR-23b in vivo and in vitro. The rats were subjected to CLP 7 days after transfection. Cardiac function, inflammatory response, and heart tissues were examined 3 days thereafter. In an in vitro experiment, H9C2 cardiomyoblasts were stimulated with lipopolysaccharide (LPS) after transfection of miR-23b, following which apoptosis and the level of NF-κB were analyzed. The expression of miR-23b was upregulated during polymicrobial sepsis, and transfection of miR-23b lentivirus improved the outcome of sepsis-induced cardiomyopathy by attenuating inflammatory responses and protecting against histopathological damage. In in vitro experiments, elevated miR-23b inhibited excessive apoptosis of cardiomyocytes, which may be because activation of the NF-κB signaling pathway was inhibited by the decreased levels of TRAF6 and IKKβ. Therefore, miR-23b improved sepsis-induced cardiomyopathy by attenuating the inflammatory response, suppressing apoptosis, and preventing NF-κB activation via targeted inhibition of TRAF6 and IκκB. These results indicated that miR-23b may represent a novel therapeutic approach for clinical treatment of sepsis-induced cardiomyopathy.