Hypervirulent Klebsiella pneumoniae (hvKP) causes invasive infections, including bloodstream infections and liver abscesses, and dysregulated host inflammation may exacerbate liver injury. We investigated whether pretreatment with Humanin, a mitochondria-derived anti-inflammatory peptide, could attenuate hvKP-associated liver injury. We measured serum Humanin in 20 patients with hvKP-associated bloodstream infection and liver abscess and 20 matched healthy controls. C57BL/6 mice received intraperitoneal Humanin (2.5 or 5 mg/kg/day) for five days before intravenous hvKP challenge. We assessed liver injury, inflammatory responses, hepatic transcriptomes, NF-κB activation, and survival. Serum Humanin was higher in patients than in the controls (p < 0.001). In infected mice, Humanin pretreatment was associated with less prominent histopathological liver injury and lower serum ALT, AST, and PCT, hepatic myeloperoxidase activity, F4/80 immunoreactivity, CD86 fluorescence, and pro-inflammatory gene expression. The effects were generally greater at 5 mg/kg than at 2.5 mg/kg. Transcriptomic analysis showed attenuation of inflammatory pathways, including NF-κB signaling (NES = −1.86, p = 0.002, FDR = 0.012). Humanin also reduced p-p65/p65 and p-IκBα/IκBα ratios in liver tissue and hvKP-stimulated bone-marrow-derived macrophages; 5 mg/kg prolonged survival (p < 0.05). Humanin pretreatment may therefore limit inflammatory liver injury during systemic hvKP infection. This effect was associated with reduced macrophage-associated inflammation and NF-κB activation, although its molecular targets remain unknown.