Large-scale infrastructure projects such as ports can have a significant impact on the development of nearby cities. While economic benefits of the port spill over to other regions, often internationally operating firms, port-cities experience negative externalities like environmental and land use issues and traffic congestion. Traditional port impact studies are expensive, and offer a static picture that doesn’t take into account the complex adaptive nature of the port-city system. There is a need for a comprehensive dynamic model of port-city development, incorporating beneficial and negative externalities of port infrastructure development on the city and peri-urban green space. A system dynamics modelling study is performed using the case study of Tema and its port on the Gulf of Guinea in Ghana, to evaluate interventions for sustainable port-city development in an African context. A model is conceptualized and specified, based on Forrester’s Urban Dynamics model, fit to cope with relative scarcity of available data. It incorporates and explicitly models road transport congestion, informal settlement and green space encroachment, as well as port infrastructure. Model testing and use show that the model is fit for the purpose of exploring the long term impacts of port infrastructure investments on the port-city system. Interventions aiming at sustainable development are simulated and evaluated for their performance. Recommendations regarding interventions and the potential future use of the model with stakeholders are made.