Systems and methods for opportunistic cross radio access technology (RAT) bandwidth allocation are disclosed. The system comprises wireless wide area network (WWAN) radio configured to be used as a primary cell (PCell) to communicate with a dual mode mobile wireless device on a licensed band and a wireless local area network (WLAN) radio integrated with the WWAN radio and configured to be used as a secondary cell (SCell) to provide additional wireless connectivity to the dual mode mobile wireless device in an unlicensed band that is controlled by the PCell. The PCell provides network access and mobility control for the dual mode mobile wireless device and also supports an opportunistic cross carrier bandwidth allocation through a cross RAT coordination module in the downlink and uplink of the SCell in the unlicensed band.