Background: Autosomal dominant polycystic kidney disease (ADPKD) is characterized by multiple bilateral kidney cysts which gradually enlarge, resulting in a decline in kidney function. Cyst growth is significantly driven by ATP-dependent chloride secretion mediated by the ion channel TMEM16A. This pathway is further augmented in advanced stages of the disease by hypoxia and activation of the hypoxia-inducible factor (HIF) 1α. The mechanisms by which ATP leads to activation of TMEM16A and how HIF-1α contributes to cyst growth in vivo have remained elusive. Methods: Mice with an inducible tubule-specific deletion of Pkd1 were compared to mice with an additional co-deletion of the purinergic receptor P2y2r. Furthermore, animals were challenged by pharmacological activation of HIF-1α and Pkd1-deficient mice were treated with suramin, an antagonist of purinergic signaling. In addition, expression of P2Y2R, TMEM16A and HIF-1α was analyzed in nephrectomy samples from 27 ADPKD patients. Results: Genetic deletion of P2y2r significantly inhibited cyst growth in vivo. In addition, aggravation of the polycystic phenotype mediated by pharmacological activation of HIF-1α was reduced by deletion of P2y2r. Application of suramin in order to pharmacologically inhibit purinergic signaling also suppressed cyst enlargement in vivo. Analysis of kidney samples from 27 ADPKD patients revealed significant expression of P2Y2R at the luminal site of the cyst-lining epithelium. Conclusions: P2Y2R was significantly expressed in human and mouse polycystic kidneys. Deletion and antagonism of P2Y2R reduced cyst enlargement in an ADPKD mouse model.