Embodiments of the invention provide novel solutions, including systems, methods and/or software, for providing handoffs between cellular providers and VoIP providers. In some cases, for example, upon the initiation of a call from a dual-mode cellular phone, the cellular network (and/or a component thereof) may be configured to store the dialed number and/or substitute a predetermined number for the dialed number. The predetermined number may be associated with a VoIP provider's system. Hence, in a particular embodiment, the call may be routed (e.g., via the PSTN) to the VoIP provider's system, which may be configured to obtain (perhaps from an application server) the original dialed number and/or to route the call (e.g., via the PSTN) to the original dialed number. If the dual-mode phone subsequently obtains IP access, a VoIP connection may be established between the VoIP system and the phone and/or a handoff may be performed (e.g., in the VoIP system) to transfer the call from the cellular connection to the VoIP connection. Optionally, the cellular connection may be terminated.