The effects of transcranial electrical stimulation (tES) have been documented for a variety of mental functions, including numerical cognition. This article first reviews 2 prominent forms of tES, transcranial direct current stimulation (tDCS) and transcranial random noise stimulation (tRNS). This is followed by an assessment of the applications of this technology in the enhancement of aspects of numerical cognition, including numerosity, magnitude representation, and more complex arithmetic operations. The review concludes with discussions of directions for future research. These include the need to take individual differences into account in experimental designs, extending research to individuals with difficulties and deficits in working with numbers, the need to consider potential cognitive costs that may offset cognitive benefits of tES. A recurring theme in this article is the need to move toward greater ecological validity of experimental findings.