The frequency diverse array (FDA) technology plays an important role in covert communication. In this letter, we consider a FDA-aided covert communication system with multiple illegitimate wardens. To maximize the covert rate, we jointly optimize the transmit beamformer and frequency offsets at the array antenna, subject to the covert constraints at different wardens. In particular, we propose to utilize a modification of the block successive upper bound minimization (BSUM) algorithm to solve this optimization problem. Simulation results demonstrate that our proposed FDA scheme can significantly enhance covert performance.