Activation of G protein-coupled estrogen receptor 1 (GPER1) elicits antihypertensive actions in different animal models. The endothelin-1 signaling system plays a fundamental role in blood pressure regulation. Lack of functional endothelin receptor B (ET) evokes hypertension and salt sensitivity. GPER1 and ET interact to promote urinary sodium excretion in female rats. We hypothesized that activation of GPER1 protects against hypertension and salt sensitivity induced by ET antagonism in female rats. Female Sprague-Dawley rats were implanted with radiotelemetry. Animals were then subjected to ovariectomy and simultaneously implanted with minipumps to deliver either the GPER1 agonist G1 or its corresponding vehicle. Two weeks post surgery, we initiated treatment of rats with the ET antagonist A-192621. Animals were maintained on a normal-salt diet and then challenged with a high-salt diet for an additional 5 days. Assessment of mean arterial blood pressure revealed an increase in vehicle-treated, but not G1-treated, rats in response to ovariectomy. A-192621 increased blood pressure in normal-salt diet-fed vehicle- and G1-treated rats. G1 improved the circadian blood pressure rhythms that were disrupted in A-192621-treated ovariectomized rats. Thus, although systemic GPER1 activation did not protect ovariectomized rats from hypertension and salt sensitivity induced by ET antagonism, it maintained circadian blood pressure rhythms. Functional ET is required to elicit the antihypertensive actions of GPER1. Additional studies are needed to improve our understanding of the interaction between G protein-coupled receptors in regulating circadian blood pressure rhythm. Systemic G protein-coupled estrogen receptor 1 (GPER1) activation in rats prevents the increase in blood pressure evoked by ovariectomy. Blockade of endothelin receptor B negates the blood pressure-lowering impact of GPER1 in ovariectomized rats. Endothelin receptor B plays an important role in mediating the blood pressure-lowering action of GPER1 activation in female rats.