City systems, consisting of the various social and technical infrastructures required for urban areas to function, are facing major challenges in the coming decades as global urbanization and the pressure on resource efficiency and sustainability continue. Agent-based simulation and modelling techniques enable us to study these systems from various levels of abstraction looking at actors as well as system level perspectives, and are particularly suited to understand the dynamics of underlying structures and experiment with various scenarios and the effect of local decisions on emerging system properties. This special issue aims to showcase innovative use of agent-based modelling (ABM) and multi-agent system (MAS) approaches for effective decision support regarding urban innovations in fields linked with urban development and to explore and identify how researchers in different disciplines integrate their knowledge through agent models. We are inviting researchers from across a wide range of disciplines (including computer science, physics, engineering, economics, sociology and others) to submit papers to this special issue that exhibit state-of the art innovation in ABM/MAS applied to cities. This innovation may come in the form of computational, conceptual, analytical, participatory or epistemological advances for a range of aims and motivations associated with the challenge of combining competitiveness and sustainable urban development in city systems. Possible topics include, but are not limited to, the following:[...]