As Shanghai is a megacity and pioneer in smart city development in China, this paper used Shanghai as a megacity example to investigate smart city development over the past ten years. By collecting data from multiple sources, a case study methodology was utilized to explore Shanghai’s smart megacity development in practice. Based on the key events and phases of Shanghai’s smart city development, the practical contents were systematically investigated. The main conclusions of this research included four aspects, consisting of information infrastructure, information technology and industrial development, information perception and smart applications, and a security assurance system. Moreover, a conceptual framework for Shanghai’s smart city development was constructed by integrating the phases and contents. Furthermore, the implications of Shanghai’s smart city development are critically discussed and identified from five aspects, including the development pathway, the government’s role, the financing channel, information and communication technology (ICT)-driven development, and a people-oriented concept. This study benefits academia, governments, and practitioners by providing useful insights and valuable implications for other cities to develop smart cities.