This paper investigates the multiplexing of unpowered wireless antenna sensors for crack monitoring at multiple locations. Four antenna sensors were multiplexed to form two sets of dual-antenna sensor arrays based on two multiplexing principles, namely the frequency division and spatial division principles. Taking advantage of frequency division, two antenna sensors operating at different frequencies can be simultaneously interrogated. The spatial division enables sequential interrogation of antenna sensors installed at different locations, even if they share the same resonant frequencies. The capability of the antenna sensor array to monitor multiple crack growth in a fatigue specimen was characterized. Multiplexing antenna sensors enables us to track sub-millimeter crack growth over a large area.