Prefabricated building projects (PBPs) have been recognized as an effective method for reducing energy consumption, carbon emissions, and resource depletion. Various information, material, product, service, and fund flows exist in PBPs, leading to high requirements of information exchange and collaboration among the multiple stakeholders. The Internet of Things (IoT) platforms are powerful tools that can support these requirements. However, the IoT platforms have not been extensively applied in industry, which is a significant bottleneck in PBP promotion. Stakeholders are the entities that make decisions on the use of IoT in PBPs and play an important role in its successful implementation. This study proposes a game-theory-based model to reveal the mechanisms of stakeholders’ decision-making on the adoption of IoT platforms in PBPs. The game analysis results reveal the optimal selection strategies of critical stakeholders regarding the IoT adoption under different conditions. The market penetration rate (MPR) of IoT platforms in the PBP markets has been found to be a critical factor that influences the decisions of critical stakeholders considerably. The results of this paper could provide valuable policy implications (i.e., improving the market penetration rate of IoT platforms by developing pilot projects, motivating clients to use the platforms in PBPs, and providing relevant IoT educational programs) for promoting the adoption of IoT in PBPs, which is of benefit to enhance PBP development and further improve energy and resource conservation.