Paeoniflorin (PF), a monoterpene glucoside, is a primary bioactive component of paeony, the root extract of Paeonia lactiflora. We tested the antioxidant effects of PF and its ability to prevent lipopolysaccharide (LPS)-induced oxidative stress. We intraperitoneally administered PF (2.5, 5, or 10 mg/kg) to rats for 20 days. On day 21, we injected the rats with LPS 4 h before sacrifice and measured serum levels of glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, lactate dehydrogenase as well as the levels of malondialdehyde, superoxide dismutase, catalase, and glutathione peroxidase in liver whole-cell homogenates and mitochondrial fractions. LPS treatment increased levels of glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, lactate dehydrogenase, and malondialdehyde, but PF treatment blocked these increases. LPS treatment also decreased antioxidant levels of superoxide dismutase, catalase, and glutathione peroxidase, but PF blocked these decreases. PF also protected liver tissue, as shown by histopathology. These results suggest that PF can protect against LPS-induced liver inflammation.