AIM: The study goal was to investigate effect of amentoflavone on nuclear factor-kappaB (NF-kappaB)-modulated metastatic mechanism in osteosarcoma U2OS cells. U2OS cells were treated with amentoflavone, NF-kappaB inhibitor, protein kinase B (PKB or AKT) inhibitor or mitogen-activated protein kinase (MAPK) inhibitor. Change of cell viability, NF-kappaB activation, expression of metastasis-associated proteins, signal transduction, and cell migration and invasion were evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, NF-kappaB reporter gene assay, western blotting, and cell migration and invasion assays. The results demonstrated that inhibition of activation of extracellular signal-regulated kinases (ERK) was a key point for suppression of NF-kappaB-modulated metastatic mechanism. Amentoflavone significantly inhibited NF-kappaB activation, ERK phosphorylation, expression of metastasis-associated proteins, and cell migration and invasion. Our findings indicate that amentoflavone reduces metastatic potential through suppression of ERK and NF-kappaB activation in osteosarcoma U2OS cells.