Background and PurposeCoronary artery disease leads to ischaemic heart disease and ultimately myocardial infarction. Thus, it is important to determine the factors that regulate coronary blood flow. Ca2+‐activated chloride channels contribute to the regulation of arterial tone; however, their role in coronary arteries is unknown. The aim of this study was to investigate the expression and function of the main molecular correlate of Ca2+‐activated chloride channels, TMEM16A, in rat coronary arteries.Experimental ApproachWe performed mRNA and protein analysis, electrophysiological studies of coronary artery myocytes, and functional studies of coronary artery contractility and coronary perfusion, using novel inhibitors of TMEM16A. Furthermore, we assessed whether any changes in expression and function occurred in coronary arteries from spontaneously hypertensive rats (SHRs).Key ResultsTMEM16A was expressed in rat coronary arteries. The TMEM16A‐specific inhibitor, MONNA, hyperpolarised the membrane potential in U46619. MONNA, T16Ainh‐A01, and Ani9 attenuated 5‐HT/U46619‐induced contractions. MONNA and T16Ainh‐A01 also increased coronary flow in Langendorff perfused rat heart preparations. TMEM16A mRNA was increased in coronary artery smooth muscle cells from SHRs, and U46619 and 5‐HT were more potent in arteries from SHRs than in those from normal Wistar rats. MONNA diminished this increased sensitivity to U46619 and 5‐HT.Conclusions and ImplicationsIn conclusion, TMEM16A is a key regulator of coronary blood flow and is implicated in the altered contractility of coronary arteries from SHRs.