A multi-input multi-output antenna system capable of being disposed in an electronic device and the electronic device including the antenna system have a low-frequency antenna assembly and a high-frequency antenna assembly. The low-frequency antenna assembly includes multiple low-frequency antennas that are spaced apart from each other by a distance. The high-frequency antenna assembly includes multiple high-frequency antennas that are spaced apart from each other by a distance. One of the high-frequency antennas is structured as a low-profile dish antenna and is located between the low-frequency antennas, so that the antenna system has smaller volume and height, and better isolation and radiation patterns.