The efficacy of anti‐angiogenic treatment by targeting VEGF/VEGF receptors in metastatic clear cell renal cell carcinoma (ccRCC) varies from patient to patient. Discovering the reasons behind this variability could lead to the identification of relevant therapeutic targets. Thus, we investigated the novel splice variants of VEGF that are less efficiently inhibited by anti‐VEGF/VEGFR targeting than the conventional isoforms. Byin silicoanalysis, we identified a novel splice acceptor in the last intron of theVEGFgene resulting in an insertion of 23 bp in VEGF mRNA. Such an insertion can shift the open‐reading frame in previously described splice variants of VEGF (VEGFXXX), leading to a change in the C‐terminal part of the VEGF protein. Next, we analysed the expression of these alternatively spliced VEGF new isoforms (VEGFXXX/NF) in normal tissues and in RCC cell lines by qPCR and ELISA, and we investigated the role of VEGF222/NF(equivalent to VEGF165) in physiological and pathological angiogenesis. Ourin vitrodata demonstrated that recombinant VEGF222/NFstimulated endothelial cell proliferation and vascular permeability by activating VEGFR2. In addition, VEGF222/NFoverexpression enhanced proliferation and metastatic properties of RCC cells, whereas downregulation of VEGF222/NFresulted in cell death. We also generated anin vivomodel of RCC by implanting RCC cells overexpressing VEGF222/NFin mice, which we treated with polyclonal anti‐VEGFXXX/NFantibodies. VEGF222/NFoverexpression enhanced tumour formation with aggressive properties and a fully functional vasculature, while treatment with anti‐VEGFXXX/NFantibodies slowed tumour growth by inhibiting tumour cell proliferation and angiogenesis. In a patient cohort from the NCT00943839 clinical trial, we investigated the relationship between plasmatic VEGFXXX/NFlevels, resistance to anti‐VEGFR therapy and survival. High plasmatic VEGFXXX/NFlevels correlated with shorter survival and lower efficacy of anti‐angiogenic drugs. Our data confirmed the existence of new VEGF isoforms that could serve as novel therapeutic targets in patients with RCC that are resistant to anti‐VEGFR therapy.