Systems and methods for radar altimeter antenna performance monitoring via reflected power measurements are provided. In one embodiment, a single antenna radar altimeter comprises: an antenna; a circulator coupled to the antenna; a transmitter coupled to the circulator; a receiver coupled to the circulator; wherein the circulator provides coupling of the transmitter and the receiver to the antenna while providing isolation between the transmitter and the receiver; a reflected power monitor positioned between the circulator and receiver; and a processor coupled to the reflected power monitor via a first analog-to-digital converter, the processor configured to compute and track reflected power measurement statistics from data generated by the reflected power monitor and provide a performance output indicating when one or more of the reflected power measurement statistics exceed a predetermined deviation threshold.