A mobile wireless communications device includes a housing and main circuit board carried by the housing and having circuitry thereon. A keyboard circuit board is carried by the lower portion of the housing and has a keyboard section and keyboard circuitry thereon connected to circuitry on the main circuit board. An antenna section on the keyboard circuit board is configured as an antenna and positioned at the lower portion of the housing and has a pattern of conductive traces forming an antenna circuit and connected to the circuitry on the main circuit board. The keyboard circuit board preferably comprises a flex circuit.