Signal transducers and activators of transcription factors (STAT)mediate many of the cellular responses that occur following cytokine, growth factor, and hormone signaling. STATs are activated by tyrosine and serine phosphorylation, which normally occurs as a tightly regulated process. However, constitutively activated STATs have been found in many human tumors as well as in v-abl- and v-src transformed cell lines. Pyk2, a member of focal adhesion kinase family and can be activated by c-Src, EGF receptor (EGFR), Janus kinase (JAK) 1, tyrosine kinases, and G-protein coupled receptor signaling. While Pyk2 has been implicated in JAK-dependent activation of MAPK and Stat1, no role for Pyk2 in the activation of other STAT proteins has been ascribed. Here, we provide evidence that Pyk2 along with c-Src facilitate EGFR-mediated Stat3 activation. Pyk2 expression in HeLa cells induces Stat3-reporter gene activation and Stat3 phosphorylation on amino acid residues Y705 and S727. Together Pyk2 and c-Src potently activate Stat3, and Pyk2 enhances Stat3 induced cell proliferation. Moreover, expression of a dominant negative version of Pyk2 impairs c-Src-induced Stat3 activation and cell proliferation. The treatment of A431 cells with EGF results in the recruitment of c-Src, Pyk2 and Stat3 to the EGFR and the phosphorylation of c-Src, Pyk2, and Stat3. Expression of constructs for dominant negative forms of either Pyk2 or c-Src impair EGF induced Stat3 phosphorylation. These results indicate that Pyk2 facilitates EGFR and c-Src-mediated Stat3 activation, thereby implicating Pyk2 activation as a potential co-mediator in triggering Stat3-induced oncogenesis.