Gram-negative bacterial infections induce inflammation and pain. Lipopolysaccharide (LPS) is a pathogen-associated molecular pattern and the major constituent of Gram-negative bacterial cell walls. Diosmin is a citrus flavonoid with antioxidant and anti-inflammatory activities. Here we investigated the efficacy of diosmin in a nonsterile model of inflammatory pain and peritonitis induced by LPS. Diosmin reduced in a dose-dependent manner LPS-induced inflammatory mechanical hyperalgesia, thermal hyperalgesia, and neutrophil recruitment to the paw (myeloperoxidase activity). Diosmin also normalized changes in paw weight distribution assessed by static weight bearing as a nonreflexive method of pain measurement. Moreover, treatment with diosmin inhibited LPS-induced peritonitis as observed by a reduction of leukocyte recruitment and oxidative stress. Diosmin reduced LPS-induced total ROS production (DCFDA assay) and superoxide anion production (NBT assay and NBT-positive cells). We also observed a reduction of LPS-induced oxidative stress and cytokine production (IL-1β, TNF-α, and IL-6) in the paw. Furthermore, we demonstrated that diosmin inhibited LPS-induced NF-κB activation in peritoneal exudate. Thus, we demonstrated, using a model of nonsterile inflammation induced by LPS, that diosmin is a promising molecule for the treatment of inflammation and pain.