A communications apparatus includes at least two cellular system radio transceivers capable of simultaneously performing transmitting/receiving radio activities in two cellular networks and a control entity. The control entity is coupled to the cellular system radio transceivers, collects radio activity information of the cellular system radio transceivers, determines whether interference will occur or is occurring and which cellular system radio transceiver is an aggressor transceiver and which cellular system radio transceiver is a victim transceiver when the interference occurs according to the radio activity information, and further determines control information according to the radio activity information for controlling the aggressor transceiver or the victim transceiver to mitigate the interference. The aggressor transceiver is the cellular system radio transceiver having the transmitting radio activity that will interfere or interferes with the receiving radio activity of the victim transceiver.