An amazing utilization of internet of things (IoT)-based smart technologies has been observed in recent years. Internet of things (IoT) became smarter and autonomous, leading the way by interconnecting and interacting with the environment. Existing technologies such as big data, AI, and cloud computing have been supported by IoT but with some limitations. Blockchain is the better solution to access and share data with the decentralized system. IoT spreads its applications in healthcare, industrial internet of things, supply chain management, traffic management, etc., out of which smart cities take special attention in recent days by integrating with IoT to create a sustainable ecosystem by using information and communication technology (ICT). Smart cities can offer various smart applications for boosting the life prominence of society. These characteristics of blockchain are beneficial to the creation of smart cities. In this regard, the authors have conducted a systematic review of articles. This study highlights the integration of blockchain with IoT.