Instant messaging (IM) is one of the most popular Web 2.0 tools for the facilitation of synchronous communication, collaboration, and social interaction among users. The chances that incumbent instant messaging (IM) users will suffer from involuntary switching have increased because competition can eliminate their service/technology providers. This concern leads to our research question: what factors influence IM users’ decision-making in involuntary switching? In light of the above concerns, this study aims to extend the push–pull–mooring (PPM) framework and the migration theory to the context of service involuntary switching by incorporating the notions of network effects and regret. Our model theorizes that four constructs of network effects (referent network size, future expectation, perceived complementary, and perceived compatibility), similarity and innovativeness (pull factors), switching cost (mooring factors), and three push factors regarding migration plan and outcome (dissatisfaction with technical quality and information quality of the migration plan and regret) can affect users’ intention to migrate to other IM services and subsequently alter their migration behaviors. This hypothetical model used in this study has been empirically validated using data collected from 381 IM users. Implications for theory and practice are also discussed.