Camelina [Camelina sativa (L.) Crantz] seed has long been consumed as a source of food in Canada. But limited information is available concerning the systematical evaluation of the composition, content, and antioxidant activity of Camelina seed polyphenol extract (CSPE). Therefore, the aim of this study was to identify, quantify and evaluate the antioxidant activity of CSPE. The result showed that eight compositions were identified and determined by the UPLC-DAD-ESI-MS² analysis. CSPE has potent free radical scavenging capacity. CSPE treatment significantly increased the activities of the antioxidant enzymes (superoxide dismutase and catalase) and glutathione content in a dose-dependent manner in RAW264.7 cells with oxidative injury and also reduced malondialdehyde content (P < 0.01). It may be concluded that CSPE has a strong antioxidant activity as depicted by the in vitro experiments and thus possesses the potential to be developed as food antioxidants or as an ingredient in functional foods. Graphical Abstract