The feedback mode of the scanning electrochemical microscope (SECM) is used to induce and measure charge-transfer coupling (CTC) between two ion-transfer (IT) processes across liquid/liquid interfaces. Results are interpreted using a general model for coupling processes under steady-state conditions that is also applicable to other modes of coupling such as IT-ET and ET-ET (ET = electron transfer). The measured feedback curves demonstrate the effect of mass-transfer limitations in these processes on the potential across the interface, shedding new light on the dynamics of bioenergetics and phase-transfer catalysis systems as well as on previous SECM studies of liquid/liquid interfaces.