Although mutations in Kras are present in 21% of lung tumors, there is a high level of heterogeneity in phenotype and outcomes amongst lung cancer patients suggesting the importance of other pathways. Wnt/-catenin signaling is a known oncogenic pathway that plays a well defined role in colon and skin cancer but its role in lung cancer remains unclear. We show that activation of Wnt/-catenin in the bronchiolar epithelium of the adult lung does not promote tumor development by itself. However, activation of Wnt/- catenin signaling leads to a dramatic increase in tumor formation both in overall tumor number and size compared to KrasG12D alone. We show that activation of Wnt/- catenin signaling significantly alters the KrasG12D tumor phenotype resulting in a phenotypic switch from bronchiolar epithelium to the highly proliferative distal progenitors found in the embryonic lung. This is associated with a decrease in E- cadherin expression at the cell surface which may increase metastasis in Wnt/-catenin signaling positive tumors. Together, these data suggest that activation of Wnt/-catenin signaling in combination with other oncogenic pathways in lung epithelium may lead to a more aggressive phenotype due to the imposition of an embryonic distal progenitor phenotype accompanied by decreased E-cadherin expression.