© 2019 IEEE. A new technique for the estimation of coupling between array elements in MIMO transceivers is presented. The estimation method is founded on subsequent transmission and over-the-air (OTA) reception between the array elements, when the transmitter's characteristics are unknown. The method enables accurate on-line characterization of the behavior of the array in terms of coupling for a complete system with PAs and antennas connected. The method is validated via OTA measurements on a four-element array in a MIMO transmitter configuration. The results demonstrate that the estimated couplings with the proposed technique are similar to the ones obtained from S-parameter measurements with deviations reflecting the operation with antennas and PAs connected. The proposed intra-array coupling estimation facilitates practical OTA measurement-based modeling and linearization of MIMO transmitters.