This paper presents the results of a study to investigate the performance of an integrated urban wastewater system (IUWS) consisting of a sewer system, biological wastewater treatment plant and receiving water under future climate change and urbanisation. In particular, the roles of both system operational control and (re)design were studied as means to ensure future compliance of the system with recipient water quality standards. This is carried out by applying a scenario-based approach to describe the possible features of future climate change and/or urbanisation. Dissolved oxygen and ammonium concentrations are considered as the objectives of the optimisation models. Critical flow rates in the IUWS are considered as decision variables of the operational control model and sewer storage tank volume is considered as the design model decision variable in this study. It is demonstrated that operational control optimisation alone, under all the scenarios developed, does not have enough potential to cope with these future conditions and only when combined with design optimisation can adequate performance be guaranteed.