Infrastructure mega-project (IMP) innovation is a complex process characterized by highly diverse innovators, a dynamic life-cycle, and stickiness of innovation knowledge. The IMP’s innovation network can be easily broken due to the fact that the network involves many different innovators across different industries and different projects. Further reasons for the fragility of the IMP’s innovation network are the dynamics of the IMP life-cycle, the diversity of the IMP’s innovative entities, the uniqueness of each IMP, and the temporary nature of each IMP’s organizations. The innovation island formed by the breaking of an IMP’s innovation network can stifle and harm innovation performance. Drawing from the knowledge-based view as well as innovation network theory, our research identifies the heterogeneous characte- ristics of IMP innovation. We propose a framework to analyze the formation mechanism of the IMP innovation island from three dimensions—the horizontal innovation island, the vertical innovation island, and the longitudinal innovation island. We look at the Hong Kong-Zhuhai-Macao Bridge project to elaborate the innovation island concept that negatively impacts IMP innovation. We also offer theoretical implications regarding the broader question of how IMPs can manage their innovation in practice.