The evolution of autonomous vehicles necessitates robust, high-speed, and low-latency wireless communication systems. This paper presents a novel high-gain Multiple-Input Multiple-Output (MIMO) beamforming antenna system that concurrently supports Dedicated Short Range Communications (DSRC) at 5.9 GHz and millimeter-wave (mmWave) 5G communications at 28 GHz. The proposed design addresses challenges such as compactness, dual-band operation, beam steering capability, and port-to-port isolation within dynamic vehicular environments. The antenna system comprises dual-band patch arrays with dedicated feed networks, achieving peak gains of 7.4 dBi for DSRC and 10.8 dBi for mmWave 5G. Fullwave simulations and experimental validations demonstrate the system’s efficacy in real-time vehicular scenarios, highlighting its potential for enhancing V2X communications in autonomous vehicles.