This study investigates the vulnerability of the wastewater collection and disposal infrastructure to sea-level rise in eThekwini Municipality, South Africa. By using geographical information systems (GIS) and a multi-criteria analysis considering elevation, operational capacity and connectivity, a scale of vulnerability was established and the most vulnerable infrastructural elements were identified in the municipality. These should be prioritised for detailed monitoring and adaptive interventions in order to maintain the functionality of the wastewater system as sea level is predicted to rise.