A communications apparatus includes a plurality of communications circuits and a coexistence management circuit. Each communications circuit is configured to provide wireless communications services in compliance with a protocol. The coexistence management circuit is configured to manage radio activities of the communications circuits. In response to a detection result of at least two radio activities to occur in a subsequent packet time, the coexistence management circuit is configured to determine whether an interference signal related to said at least two radio activities falls in a predetermined frequency band, and when the interference signal falls in the predetermined frequency band, the coexistence management circuit is configured to adjust a transmission power or an execution time of one of said at least two radio activities.