We show that the transcriptional repressor Tel plays an evolutionarily conserved role in angiogenesis: it is indispensable for the sprouting of human endothelial cells and for normal development of the Danio rerio blood circulatory system. Tel orchestrates endothelial sprouting by binding to the generic co-repressor, CtBP. The Tel-CtBP complex temporally restricts a VEGF (vascular endothelial growth factor)-mediated pulse of dll4 expression and thereby directly links VEGF receptor intracellular signalling and intercellular Notch-Dll4 signalling. It further controls branching by regulating expression of other factors that constrain angiogenesis such as sprouty family members and ve-cadherin. Thus, the Tel-CtBP complex conditions endothelial cells for angiogenesis by controlling the balance between stimulatory and antagonistic sprouting cues. Tel control of branching seems to be a refinement of invertebrate tracheae morphogenesis that requires Yan, the invertebrate orthologue of Tel. This work highlights Tel and its associated networks as potential targets for the development of therapeutic strategies to inhibit pathological angiogenesis.