Phosphoproteomic analysis of a xenograft-derived, isogenic cell line model revealed WBP2 transcription co-activator to be a novel EGFR tyrosine kinase substrate that is associated with breast cancer development. Overexpression of WBP2 phosphomimic mutant in ER+ MCF7 mammary cancer epithelial cells conferred growth-factor independence and aggressive traits that were concomitant with increased ER and TCF reporter activities suggesting a mechanism involving WBP2-mediated Wnt and ER activation. WBP2 knock down abolished the Wnt3a-induced growth, migratory and invasive properties of triple-negative, high-WBP2-expressing MDA-MD-231 breast cancer cell line, concomitant with a reduction in responsiveness to Wnt3a activation, an effect that could be rescued in part by WBP2 re-expression. Co-expression of b-catenin and WBP2 enhanced the Wnt activation compared to b-catenin overexpression alone. WBP2, in turn, is regulated in a positive fashion by Wnt signalling. Since WBP2 interacts with TAZ and YAP, which are negatively regulated by the Hippo pathway and shown to participate in Wnt signaling, we also examined the role of Hippo on WBP2-mediated Wnt activation. Overexpression of the Hippo core kinase cassette diminished Wnt3a-induced, WBP2-mediated TCF reporter activity by negatively regulating WBP2, suggesting that the Hippo pathway exert a negative effect on the Wnt pathway in part by blocking WBP2 function. Our data support the notion that WBP2 may yet be another target through which the Hippo pathway antagonizes, in addition to TAZ and YAP, to regulate the Wnt pathway.