Infrastructure systems, such as those that generate and transmit energy, process waste water and enable the transportation of people and goods, provide fundamental services that underpin modern society. The simulation model integration framework (smif) is an open source Python package which supports the coupling and running of infrastructure simulation models as a system-of-systems. smif connects individual simulation models – written in different programming languages and using different methods of data input and output – allowing users to compose a system-of-systems with explicit configuration of the connections and data transformations between models. Users can then run system-of-systems models using various data sources in order to explore the effects of uncertainty in external factors and model parameterisations, and to test alternative approaches to long-term decision-making and planning across the connected models.