A mobile wireless communications device may include a portable housing, a printed circuit board (PCB) carried within the portable housing, and wireless communications circuitry carried by the PCB within the portable housing. The device may also include a folded monopole antenna assembly coupled to the wireless communications circuitry. The folded monopole antenna assembly may include a dielectric body adjacent the PCB and having a generally rectangular shape defining opposing top and bottom faces, opposing first and second end faces, and opposing first and second side faces. The antenna may also include a conductive trace coupled to the wireless communications circuitry and having a first end section extending along the first end face, a second end section extending along the second end face, and an intermediate section extending along the top, bottom, first side and second side faces.