Objective: It is unclear whether nucleophosmin (NPM) participates in cardiovascular disease. The present study aimed to investigate the role and underlying mechanisms of NPM in atherosclerosis. Methods: Levels and location of NPM in human carotid atherosclerotic plaques and healthy controls were detected by real-time polymerase chain reaction, immunoblots, and immunofluorescence. Atherosclerotic prone ApoE-/- mice were fed with a Western diet for 16 weeks as an in vivo model. Human primary umbilical vein endothelial cells (HUVECs) were cultured as an in vitro model. Results: Compared with controls, we found that NPM levels in human carotid atherosclerotic plaques were more than twice as high as in normal arteries, which mainly localized in endothelial cells. In vivo, adenovirus-containing NPM small hairpin RNA attenuated atherosclerotic lesion and promoted plaque stabilization in ApoE-/- mice fed a Western diet by reducing vascular inflammation, maintaining endothelial function, and decreasing macrophage infiltration. Furthermore, NPM knockdown decreased nuclear factor-kappa B (NF-kappa B) p65 phosphorylation. In cultured HUVECs, palmitic acid increased the protein levels of NPM and induced the expression of inflammatory cytokines and monocyte adhesion, whereas NPM knockdown attenuated this effect. In HUVECs, NPM protein physically interacted with NF-kappa B p65 subunit and promoted its nuclear transposition. NPM also increased the transcriptional activity of NF-kappa B p65 promoter and enhance its binding to target genes, including interleukin-1 beta, interleukin-6, intercellular adhesion molecule-1, and E-selectin. Conclusions: These data provide novel evidence that NPM promotes atherosclerosis by inducing vascular inflammation and endothelial dysfunction through the NF-kB signaling pathway and suggest that NPM may be a promising target for atherosclerosis prevention and treatment.