A CMOS 28-GHz phased-array beamformer chip supporting dual-polarized MIMO operation is introduced with cross-pol. leakage cancellation technique. More than 40-dB cross-pol. isolation is maintained along the TX array to the RX array. With the improved cross-pol. isolation, 2×2 DP-MIMO communication with two 5G NR OFDMA-mode streams in 256QAM is achieved in the OTA measurement. The corresponding TX-to-RX EVM is 3.3%.