Abstract: The phytohormone abscisic acid (ABA) triggers rapid stomatal closure in response to drought stress. A plethora of plasma membrane- and tonoplast-localized ion channels and transporters have been characterized as key downstream effectors of the ABA signaling cascade in guard cells. This paper provides an overview of the predominant ion channels and transporters involved in stomatal responses to ABA, with a focus on their molecular patterns and underlying regulatory mechanisms. This review also discusses the potential of genetic engineering of these molecules for improving crop water-use efficiency.