Whole flaxseed and its derived lignans have shown anti-cancer properties in a variety of malignancies. However, their potential remains uninvestigated in lung cancer, the leading cause of cancer-related deaths worldwide. We investigated the anti-tumor effects of flaxseed-derived mammalian lignan enterolactone (EL) in human lung cancer cell cultures and the chemopreventive potential of 10% whole flaxseed in a mouse model of lung carcinogenesis. We found that EL inhibits in vitro proliferation and motility of a panel of non-small cell lung cancer cell (NSCLC) lines. EL-mediated inhibition in lung cancer cell proliferation was due to a decrease in mRNA and protein expression levels of G1-phase cell cycle promoters and a simultaneous increase in mRNA and protein expression levels of p21WAF1/CIP1, a negative regulator of the G1-phase. Similarly, EL decreased lung cancer cell motility by modulating cytoskeleton organization, inhibiting the activation of the FAK-Src-paxillin signaling cascade, and expression of down-stream motility regulators. Our in vivo investigation revealed that 10% whole flaxseed reduced the incidence, number, and size of lung tumor nodules in A/J mice exposed to the tobacco smoke carcinogen, nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). RNA sequencing revealed altered expression of genes whose products modulate inflammation and oxidative stress, and are likely to be responsible for chemopreventive potential of whole flaxseed. The results from our in vitro studies highlight the anticancer potential of EL in lung cancer, while the results from our in vivo study show that whole flaxseed holds promise as a chemopreventive dietary agent in lung.