A mobile wireless communications device includes a housing and circuit board carried by the housing. RF circuitry and a processor are operative with each other and carried by the circuit board. A receiver speaker and microphone are carried by the housing. Audio circuitry is carried by the circuit board and operative with the RF circuitry and processor. A microphone audio switch and receiver speaker audio switch are carried by the circuit board and are connected with audio connection lines that interconnect the processor. A filter is operative with the audio connection lines and operatively connected to at least one of the microphone audio switch or receiver speaker audio switch to reduce conducted and radiated interfering RF energy from coupling into the audio circuitry.