A method and system for providing a short message service (SMS) between a cellular mobile communication network and an IEEE 802.11 WLAN are provided. To provide the SMS between the mobile communication network and the WLAN, a short message gateway (SMGW) is further provided between existing SS7 network and IP network. A mobile terminal (MT) connected to the cellular network is allocated radio resources by a base transceiver station (BTS). One or more BTSs are connected to a mobile switching center (MSC) through a base station controller (BSC). The MSC is connected to an SMS center (SMSC), a home location register (HLR), and the SMGW through the SS7 network. An MT connected to the WLAN is wirelessly connected to an access point (AP) and one or more APs are connected to the IP network and the SMGW through an access router (AR).