Background and Purpose Ca2+ influx via TRPV4 triggers Ca2+ release from the IP3-sensitive internal store to generate repetitive oscillations. While mitochondria are acknowledged regulators of IP3-mediated Ca2+ release, how TRPV4-mediated Ca2+ signals are regulated by mitochondria is unknown. We show that depolarised mitochondria switch TRPV4 signalling from relying on Ca2+-induced Ca2+ release at IP3 receptors, to being independent of Ca2+ influx and instead mediated by ATP release via pannexins. Experimental Approach TRPV4 evoked Ca2+ signals were individually examined in hundreds of cells in the endothelium of rat mesenteric resistance arteries using the indicator Cal520. Key ResultsTRPV4 activation with GSK1016790A(GSK) generated repetitive Ca2+ oscillations that required Ca2+ influx. However, when the mitochondrial membrane potential was depolarised, by the uncoupler CCCP or complex I inhibitor rotenone, TRPV4 activation generated large propagating, multicellular, Ca2+ waves in the absence of external Ca2+. The ATP synthase inhibitor oligomycin did not potentiate TRPV4 mediated Ca2+ signals. GSK-evoked Ca2+ waves, when mitochondria were depolarised, were blocked by the TRPV4 channel blocker HC067047, the SERCA inhibitor cyclopiazonic acid, the phospholipase C (PLC) blocker U73122 and the inositol triphosphate receptor (IP3 R) blocker caffeine. The Ca2+ waves were also inhibited by the extracellular ATP blockers suramin and apyrase and the pannexin blocker probenecid. Conclusion and Implications These results highlight a previously unknown role of mitochondria in shaping TRPV4 mediated Ca2+ signalling by facilitating ATP release. When mitochondria are depolarised, TRPV4-mediated release of ATP via pannexin channels activates plasma membrane purinergic receptors to trigger IP3 evoked Ca2+ release.