The Internet of Things (IoT) offers new opportunities for cities to make citizens live and work in more sustainable, healthy, and safe places. Since IoT applications in smart cities are characterized by different devices, networking standards, and data management strategies, trust becomes a fundamental issue in the IoT ecosystem. The explosion of IoT devices, along with their decentralized deployment, constraint resources, limited computational and cryptographic capabilities, brings challenges to trust management in IoT. The coexistence of multiple IoT domains also raises challenges, for example, how to evaluate and maintain trust across domain boundaries. This special issue aims at bringing the researchers from both academia and industry together to disseminate their recent advances related to the challenges and solutions in building trustful IoT for smart cities.