A Fine Time Measurement (FTM) authentication system and method include performing a FTM transaction comprising at least one FTM-ACK message pair transmitted and received via a first communication channel between two endpoints, where the at least one FTM-ACK message pair contains timestamp values of message departure time and message arrival time during the FTM transaction. At least one authenticating value indicative of timestamp values of the at least one FTM-ACK message pair arrival and departure times during the FTM transaction is then transmitted via a second communication channel. FTM timestamp values are recovered from the received at least one authenticating value, which are compared with the received FTM timestamp values. The received FTM timestamp values can be authenticated if there is a match between the recovered FTM timestamp values and the received FTM timestamp values.