Agrimonia pilosa Ledeb. has long been used for a useful natural agent ameliorating inflammation related symptoms in the folk medicine recipe. This study was performed to investigate effects of Agrimonia pilosa Ledeb.(AP) on the expression of inflammation related genes such as the inducible nitric oxide synthase (iNOS) in macrophage cell line, RAW 264.7 cells. The AP (whole plants) was extracted with 80% ethanol and sequentially partitioned with solvents in order to increase polarity. Among the various solvent extracts of AP, the n-butanol (BuOH) fraction showed the most powerful inhibitory ability against nitric oxide (NO) production in lipopolysaccharide (LPS)-induced RAW 264.7 cells without affecting cell viability. Reverse transcriptase-polymerase chain reaction and Western blot analysis revealed that the BuOH fraction provided a primary inhibitor of the iNOS protein and mRNA expression in LPS-induced RAW 264.7 cells. The DPPH and OH radical scavenging activities of the several fractions of 80% ethanol extracts of AP significantly increased by EtOAC and BuOH fractions. Thus, the present study suggests that the response of a component of the BuOH fraction to NO generation via iNOS expression provide an important clue to elucidate anti-inflammatory mechanism of AP.