The (Pro)renin receptor ([P]RR), also known as ATP6AP2, is a single-transmembrane protein that is implicated in a multitude of biological processes. However, the exact role of ATP6AP2 during blood vessel development remains largely undefined. Here, we use an inducible endothelial cell-specific (EC-specific) Atp6ap2-KO mouse model to investigate the role of ATP6AP2 during both physiological and pathological angiogenesis in vivo. We observed that postnatal deletion of Atp6ap2 in ECs results in cell migration defects, loss of tip cell polarity, and subsequent impairment of retinal angiogenesis. In vitro, Atp6ap2-deficient ECs similarly displayed reduced cell migration, impaired sprouting, and defective cell polarity. Transcriptional profiling of ECs isolated from Atp6ap2 mutant mice further indicated regulatory roles in angiogenesis, cell migration, and extracellular matrix composition. Mechanistically, we provided evidence that expression of various extracellular matrix components is controlled by ATP6AP2 via the ERK pathway. Furthermore, Atp6ap2-deficient retinas exhibited reduced revascularization in an oxygen-induced retinopathy model. Collectively, our results demonstrate a critical role of ATP6AP2 as a regulator of developmental and pathological angiogenesis.