The effect of counter electrode curvature on the onset voltage and spray angle of the electrospray in the cone-jet mode is experimentally investigated. Six counter electrodes, including a conventional flat electrode, and five curved (both concave and convex) electrodes are considered. The curvature of the curved electrodes was in the range of 10-33.3 m(-1). The applied voltage, the voltage range of the cone jet mode, and geometrical features such as the liquid cone length and spray angle are measured. It was observed that the ground electrode curvature could manipulate the electric field and equipotential lines in a way that results in higher or lower onset voltage of the cone-jet mode for convex and concave electrodes, respectively. In addition, the operating range or "stability island" grows by convex electrodes and decreases by concave electrodes. Simulation of electric potential lines is introduced to explain this effect further. In general, the ground electrode shape can intensify or abate the density of the equipotential lines in the vicinity of the liquid meniscus at the capillary tip. The cone jet mode onset voltage equation is modified to include this effect. Moreover, the spray shape was affected by the curved electrodes. In both configurations, the spray angle increases; however, in the case of the concave electrodes, the actual spray coverage is much closer to the theoretical spray coverage.