In this article, mainlobe deceptive jammer mitigation for multiple targets is investigated using a subaperture-frequency diverse array-multiple-input multiple-output (MIMO) radar. At the modeling stage, the transmit array is divided into multiple overlapped subapertures consisting of fully overlapped secondary subarrays, where a small frequency increment is introduced among different subapertures, while a phase coding modulation is adopted among different secondary subarrays. In this respect, all targets and jammers can be separated in a 3-D space-time cube, including the transmit spatial domain, the slow-time pulse domain, and the receive spatial domain. In this case, the problem of jammer mitigation is formulated, and a two-stage beamforming method is proposed, where the jammers with delayed pulses are first suppressed, and the jammers, which are located within the same transmit pulse, are further mitigated. Specifically, an alternating procedure is developed by transforming the suppression problem into several 1-D subproblems. In order to further improve the jammer mitigation performance, the subaperture transmit weights are also designed by maximizing the worst-case output signal-to-jammer-plus-noise ratio (SJNR) resorting to an iterative successive convex approximation (ISCA) algorithm. Numerical results corroborate the effectiveness of the developed methods in mitigating mainlobe deceptive jammers for the case of multiple true targets.