Embodiments of this application provide a gateway handover method, a gateway reselection method, and a communications apparatus. The method includes: A source gateway determines to perform gateway handover on a terminal device; determines a target gateway that is to be used to serve the terminal device; and hands over the terminal device from the source gateway to the target gateway. According to the gateway handover method, the gateway reselection method, and the communications apparatus provided in the embodiments of this application, in a non-3GPP network architecture, when gateway handover needs to be performed on the terminal device, the source gateway of the terminal device or the terminal device may hand over the terminal device from the source gateway of the terminal device to the target gateway, to implement gateway handover in the non-3GPP network architecture.