Antioxidant and nitric oxide (NO) production inhibitory activities of various extracts from scouring rush (Equisetum hyemale L.) were investigated. Antioxidant assays including DPPH free radical scavenging activity, reducing power assay, metal-chelating assay, superoxide radical scavenging assay, and nitrite scavenging ability, and assays to determine total phenolic and flavonoid contents were performed. The inhibition of NO production was measured in lipopolysaccharides (LPS)-induced RAW 264.7 macrophages, and reverse transcription (RT)-PCR was used to analyse the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX-2) in RAW 264.7 macrophages. Overall, all extracts showed high phenolic content and strong DPPH radical scavenging ability. Methanol extract exhibited stronger metal-chelating activity and NO production inhibitory activity compared with other extracts. The expression of iNOS and COX-2 was obviously augmented in response to LPS. Taken together, scouring rush could be used as a suitable natural antioxidant and a source of anti-inflammatory agent.