Microwave radiation to promote the destabilization of water-in-crude oil petroleum emulsions is already an alternative technology for heating. Recent studies have suggested that microwave heating is more effective than conventional heating. This study assessed the following effects on the demulsification process: the aging of emulsions for the two types of heating (microwave and conventional), the time interval between microwave heating and the addition of a chemical demulsifier, and the time of microwave irradiation on the heating of petroleum and brine fluids. In addition, this study compared the efficiency of water separation by conventional heating and microwave heating regarding the (a) mean temperature of the emulsion and (b) temperature of water droplets. It was observed that water separation is less efficient for the two types of heating when the emulsion is subjected to aging. The efficiency of water separation using microwave heating is greater than with conventional heating when the mean temperature of the emulsion remains the same. However, they were equivalent when the temperatures of the water droplets are equal. This fact indicates that the advantage of selectively heating water droplets by microwave radiation is that the temperature of the treatment of emulsions can be reduced: the higher temperature that is located in region of interest (water droplets and the periphery) facilitates the drainage of the interfacial film and the stage of coalescence between the water droplets.