Middleware for IoT is the software technology that has been used as the basis for the development, management, and integration of both heterogeneous devices and applications in IoT environments. Despite the intended definition of a horizontal architecture approach (i.e., a common system approach to manage different application domains or verticals) for IoT middleware has been one of the main requirements by global IoT projects during the last years, the imminent arrival of 5G technology is revealing that current middleware approaches possibly will face some challenges due to new application requirements imposed by 5G (e.g., big data bandwidth and infinity, reliable, and efficient capability of networking, joining massive user experiences on mobile communications with multimedia sharing). In this way, this chapter not only presents concepts and architectural layers of IoT Middleware, but also helps in the identification of future challenges and further perspectives regarding the IoT Middleware ability to provide pervasive systems services able to cope with 5G-based application requirements in IoT environments. The intention of this chapter is to identify what will be the next step of IoT Middleware technology and also the R&D technological impact of this step toward the real maturity of 5G.