Digital twins (DT) have emerged as expected powerful tools for optimizing products, processes and services within the industry. In urban areas, DT should foster the development of innovative services to make the city even smarter. They should also respond to several key challenges such as economic development, social inclusion and adaptation to the effects of climate change. Although a significant number of papers have examined the three topics of DT, smart city and sustainability, to date, literature has paid little attention to the intersection between them. The aim of this paper is to explore the potential linkages between these three themes. To do this, a bibliometric analysis is carried out. This paper provides the main characteristics of DT for smart cities (1). It defines the concept of “sustainable smart cities” and focuses on the role and contribution of DT for urban sustainability (2). It analyzes the challenges, in terms of engineering (3) and societal (4) that DT imply for sustainability smart cities. These first insights and results are helping to fuel a debate on the place of technology in our societies and the path to be taken towards greater sustainability.