A multi-standby mobile terminal and a method for providing a host function between different networks in a multi-standby mobile terminal are provided. The method includes creating a call from a first mobile terminal, as a multi-standby mobile terminal, to a second mobile terminal on a first network and to a third mobile terminal on a second network, outputting a received voice signal through a speaker from the first mobile terminal, when the voice signal is received from one of the second mobile terminal and third mobile terminal, and, transmitting, from the first mobile terminal, the received voice signal through a loopback process to the one of the second mobile terminal and third mobile terminal that does not transmit the voice signal.