Glioblastoma multiforme (GBM) is the most common brain tumour and has the worst prognosis with an average survival of only 14.6 months, despite current standard treatment. EGFR gene amplification, mutation and re-arrangement (all of which enhance tumour growth, survival, progression and resistance to therapy) are frequently observed in primary GBM. The most common EGFR variant in GBM, the EGFRvIII, is characterised by a deletion of 267 amino acids in the extracellular domain, leading to a receptor which does not bind ligand yet is constitutively active. Together with its impaired internalisation and degradation, the EGFRvIII enhances the tumourigenic potential of GBM by activating and sustaining mitogenic, anti-apoptotic and pro-invasive signalling pathways. The majority of studies on EGFRvIII signaling focus on RAS-ERK1/2 and PI3-K-AKT networks with only a small number of reports recognising STAT3 as a potentially critical substrate of the EGFRvIII receptor. Therefore this study undertook the aim to discover the significance of the EGFRvIII-STAT3 signaling axis in GBM patient samples. We also examined the tumourigenic potential of the EGFRvIII-STAT3 signaling network specifically in GBM primary patient-derived and established cell lines. Finally, we evaluated the efficacy of a series of FDA-approved small molecular weight inhibitors that could specifically inhibit EGFRvIII driven STAT3 activity. Importantly, these findings could identify critical therapeutic agents that can target EGFRvIII positively expressed GBM.