We are delighted to celebrate the appearance of the special issue of Serdica Journal of Computing dedicated to the Internet of Things (IoT) Ecosystems. This special issue contains selected papers that are supported by the National Scientific Fund, Bulgarian Ministry of Education and Science within the KoMEIN Project No DN 02/1 and project No DN 02/11 as well as by the European Commission under grant agreement No 763566 GATE Teaming 1 Project, and by the Scientific Fund of Sofia University within project 80-10-192/24.04.2017. The Special Issue at hand intends to promote the dissemination of the projects results in form of innovative business models, architectures, Blockchain technologies and case studies pertaining to IoT ecosystems and the Future City platform that hosts, maintain and deliver a wide range of services to citizens, government and businesses through utilizing Big Data and IoT technologies.