Increasing evidence has shown that ononin, a major isoflavone, has anti-inflammatory effects on lipopolysaccharide (LPS)-induced inflammation. However, the molecular mechanisms underlying the anti-inflammatory effects of ononin are still unclear. In the present study, we investigated these effects and the underlying mechanisms of ononin on LPS-induced inflammatory responses. Mouse RAW 264.7 cells were treated with 1 μg/mL LPS and 5, 25, 50, 100 or 150 μM ononin for 18 h. Cell viability was assessed using MTT assays, and the production of nitric oxide (NO), prostaglandin E2 (PGE2) and the pro-inflammatory cytokines TNF-α, IL-1β and IL-6 in cultures was examined by Griess and ELISA analyses. qRT-PCR was performed to detect the mRNA expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX-2). Mitogen-activated protein kinases (MAPKs) and nuclear transcription factor Kappa-B (NF-κB) signalling pathway-related proteins were assessed by western blot assays. The results showed that cell viability was not significantly affected by up to 100 μM ononin. The production of NO, PGE2 and the pro-inflammatory cytokines TNF-α, IL-1β and IL-6 in the cultures, the mRNA expression of two major inflammatory mediators, COX-2 and iNOS, and the expression of phosphorylated IκB-α, ERK, JNK, and p38 MAPKs proteins in LPS-treated cells were significantly increased. These changes could be reversed by treatment with ononin in a concentration-dependent manner (P < 0.05). The results suggest that ononin has anti-inflammatory effects on LPS-induced inflammatory responses by inhibiting the NF-κB and MAPK pathways and may be a potential treatment for inflammation.