A communications apparatus includes a wireless module and a controller module is provided. The wireless module transmits and receives radio frequency signals to and from a service network via at least a first and a second component carriers. The controller module receives a first measurement configuration corresponding to the first component carrier from the service network, receives a message indicating that the first component carrier is replaced by a third component carrier from the service network via the wireless module, receives a second measurement configuration corresponding to the third component carrier from the service network via the wireless module, keeps at least one of the first and second measurement configurations in response to receiving the message, and performs measurements according to the kept measurement configuration.