<p>Rapid urbanisation and inadequate housing policies have fuelled the proliferation of informal settlements in Dar es Salaam, Tanzania, posing significant challenges for sustainable urban development. These settlements often lack essential services and reflect complex spatial and socioeconomic dynamics that require targeted analysis to inform effective urban management strategies. This study aims to identify the spatial determinants driving informal settlement expansion in Dar es Salaam from 2012 to 2022 and evaluate the effectiveness of a geographically weighted regression (GWR) model in capturing localised growth patterns. A GWR model was employed to analyse nine variables—population density, poverty, gross domestic product, proximity to roads, rivers, the ocean, the city centre, existing informal settlements, and slope—using spatial data from multiple sources. The model assessed their influence on settlement expansion across the city by leveraging R-4.2.1, and ArcGIS Pro for analysis. The results indicate that proximity to existing informal settlements and distance from rivers are significant drivers of expansion, while traditional socioeconomic factors, such as population density and poverty, exert minimal influence. The GWR model explained 77% of the variability in settlement growth, highlighting the strong spatial heterogeneity of the factors shaping informal settlement patterns. Spatial dynamics play a critical role in informal settlement expansion, necessitating spatially sensitive urban planning. Policymakers should prioritise strategic infrastructure investments and land tenure regularisation to curb uncontrolled growth and promote sustainable urban development in Dar es Salaam.</p>