A simple and effective simulation model for keyhole multiple-input multiple-output (MIMO) channels is introduced. The keyhole is modeled as a pair of transmitting and receiving antennas relaying multipath signals from the transmitter region to the receiver region. In the separated transmitter and receiver regions, the double-directional radio channel (DDRC) model is used to model the multipath scattering. Our channel simulation model specially includes the effects of the transmitting and receiving antenna arrays such as antenna gain, radiation efficiency, port reflection loss, mutual coupling, and polarization loss all into the channel matrix through direct antenna numerical calculations with no need for any additional supplementary analytical modeling or postprocessing work. The model is capable of modeling both one-keyhole or multi-keyhole channels. Simulation results have confirmed the validity and accuracy of our simulation model.