Electrospray is the process of producing droplets by an applied electric field in which charged droplets accelerate downward toward the ground electrode under the influence of electrical and gravity fields. Liquid is ionized and will be possessed the same charges when it is passing through the nozzle by means of the driven. Fine droplet formation in an electrospray process is often explained by the hydrostatic balance between two key factors of electrostatic force and surface tension. The five main forces involved in this phenomenon are viscosity, surface tension, electrical, inertial and gravity forces. The competition between these forces generates different geometrical shapes of liquid when it emits from nozzle called electrohydrodynamic (EHD) modes. Due to widespread applications of this phenomenon in different majors, studying this process can assist to have more control on produced droplets and EHD behaviors of liquid issuing from the nozzle. The electrical properties of fluid including electrical conductivity and permittivity plays an essential role since it determines the electric stresses acting on the filament surface. Fluids according to their electrical conductivity are divided to conductive, leaky dielectric and dielectric materials. To exploit the effects of electrical properties of fluid on the process, acetic acid as a conductive, ethanol by 96% purity as a leaky dielectric and toluene as a dielectric liquid have been chosen in this study. These solutions have similar physical properties except for the electrical ones. The fluid material properties with the processing conditions are used to deduce the dimensionless groups required according to the physics of electrospray. The ratio of charge relaxation time to the hydrodynamic characteristic time represents the conductivity effects, the electric capillary number is used to consider electrical field parameters including the applied voltage and the distance between two electrodes, and finally the Weber number is defined for studying the volume flow rate effects. Standard electrospray apparatus for carrying out experiments has been provided. The high speed camera capable of 1000 frames per second (fps), was used to capture visual images of the electrospray. A series of experiments were conducted to consider the role of electrical properties on the droplets diameter and EHD modes at different operational parameters such as applied voltage, distance between two electrodes and flow rate. Results show that increasing the charge relaxation time to the hydrodynamic characteristic time leads to an increase in the amount of charges migrate from the liquid mass to the interface of liquid, therefore, decreases the droplets diameter . The change of EHD modes in conductive and leaky dielectric fluids occur in lower electric capillary number in comparison to the dielectric fluid. Increasing the Weber number also increases sprayed liquid volume, so, droplets diameter increases. On the other hand, increasing the Weber number reduces the surface charge density, thus, the change of EHD modes occurs in lower electric capillary number in comparison to higher Weber number. It is also exhibited that the electric tangential stress generated in leaky dielectric fluid due to free charges affect the droplets diameter and formed EHD modes. Key words Electrospray, Droplet diameter, Electrohydrodynamic mode, Electrical conductivity