Three flavonoids were isolated from the whole plants of Waltheria indica and biological properties investigated. On the basis of their spectroscopic data, these compounds were identified as (-)-epicatechin, quercetin, and tiliroside. These flavonoids significantly and dose-dependently inhibited the production of the inflammatory mediator nitric oxide (NO), and the cytokines (tumor necrosis factor (TNF)-alpha and interleukin (IL)-12), in lipopolysaccharide (LPS) and interferon (IFN)-gamma activated murine peritoneal macrophages, without displaying cytotoxicity. The order of inhibitory activity was quercetin>tiliroside>(-)-epicatechin. Furthermore, peritoneal macrophages were pre-activated with LPS/IFN-gamma for 24 h, and the inhibitory effects of the above mentioned isolates on the production of NO were determined after a further 24 h, to address the possible mechanisms of their action. The present study supports the use of W. indica for the treatment of inflammatory diseases in traditional medicine.