A mobile wireless communications device is for a user wearing an electronic hearing aid adjacent an ear of the user and may include an upper housing and a lower housing being slidably connected together for sliding between a retracted position and an extended use position. An audio output transducer may be carried by the upper housing and accessible to the hearing aid of the user adjacent a top end of the upper housing, and an audio input transducer may be carried by the lower housing and accessible to a mouth of the user adjacent a bottom end of the lower housing. An antenna may be carried by the lower housing adjacent the bottom end thereof so that the hearing aid is further separated from the antenna when the upper and lower housings are in the extended use position to reduce undesired coupling from the antenna to the hearing aid.