Background: Non-small cell lung cancer (NSCLC) accounts for approximately 90% of lung cancers and worldwide this affects 1.37 million patients each year. Lack of actionable mutations in lung cancer presents a significant hurdle in the development of targeted therapies for this disease. The current study identifies somatically mutated ABL1 as a genetic dependency that is required to maintain lung cancer cell survival. Results: NSCLC cell lines carrying ABL1 mutations (H1915 cells homozygous for ABL1-R351W and H2210 cells heterozygous for ABL1-G340L) were sensitive to ABL inhibitors, imatinib and dasatinib. Additionally, imatinib suppressed growth of H1915-derived lung tumour xenografts. The specificity of these pharmacological responses was verified by overexpression of drug resistant ABL1 kinase, which fully rescued the drug-induced cytotoxicities both in vitro and in vivo. Furthermore, H1915 and H2110 cells, but not the control lung cancer cell lines expressing wild type ABL1, were sensitive to ABL1 knockdown, emphasising the importance of the mutated ABL1 kinases in maintaining lung tumorigenic phenotypes. Molecular dynamic simulations indicated that ABL1 mutations induce conformational changes in the kinase domain, leading to increased activity of the mutant ABL1 proteins. Specifically, R351W substitution would shift critical regions of the kinase, DFG motif and αC- helix, into a more active conformation and G340L mutation would stabilise the active kinase conformation. Consistent with these data, transient overexpression of the ABL1 mutants identified in a lung cancer cell line and in primary lung cancer samples resulted in increased downstream signalling, relative to wild type ABL1. Lastly, mutated ABL1 proteins were shown to be primarily localised to the cytosol, which is associated with the mitogenic and survival activities of the mutationally altered ABL1 kinases. Conclusion: The current study demonstrates for the first time that somatic ABL1 mutations identified in NSCLC increase kinase activity, promoting cell survival or proliferation, and these effects can be prevented by pharmacological ABL inhibition. These data suggest that NSCLC patients presenting with ABL1 mutations (approximately 1.5%) could be stratified for treatment with clinically available ABL inhibitors, such as imatinib.