This study aimed to develop a blockchain-based IoT (BIoT) system for adopting automated personalized indoor temperature control to the building management system (BMS) while ensuring data privacy and security. A novel blockchain framework was proposed to register occupants and the personalized thermal sensation vote (TSV) prediction model for training, and control indoor temperatures while ensuring the security of occupant and building data. By implementing the proposed BIoT temperature control system, it could securely transfer about 30,000 personal data for TSV prediction at the same time using a single PC. Moreover, the personalized TSV prediction model could improve accuracy compared to the existing generalized TSV prediction model. As a result, the developed BIoT temperature control system could improve thermal comfort and energy efficiency compared to manual indoor temperature control. Occupants can ultimately be satisfied with the personalized temperature control in every room where required IoT devices are installed without privacy issues.