Abstract Cities in Sub-Saharan Africa are undergoing massive spatial transformation owing to rapid urbanization. For many cities in the Global North, Latin America and Asia, spatial transformation has been traditionally characterised by a shift from monocentric to polycentric urban patterns. In the case of Sub-Saharan Africa, however, it is unclear whether the evolving spatial structure of cities conform to or are explained by existing urban geography models. This paper pursues twofold objectives: one, examines the evolution of the spatial structure of a Sub-Saharan African city-region and its relationship with mainstream urban geography models; and, two, explores the urban planning and policy implications of the spatial transformation. The study draws on spatially explicit data from Kumasi City-Region in Ghana, which is analysed with a set of spatial metrics and an urban growth model. The results indicate that, while the city-region’s urban spatial structure before the turn of the Twenty-first century largely conforms to the traditional monocentric model, it is increasingly becoming deconcentrated and dispersive, which suggests a likely pending phase of coalescence in a stochastic fractal urban growth process. Contrary to what is observed in other parts of the world, the declining monocentricity has not transformed into a polycentric urban structure, rather, urban growth is becoming amorphous. There is high level of development spontaneity that cast an image of a city-region that is charting inefficient and unsustainable spatial development path. Urban scholars would have to transcend the frontiers of existing urban structure models to better depict the spatial evolution of sub-Saharan African cities like Kumasi City-Region, while Policy makers need to re-position the Ghanaian planning system to be more influential in delivering sustainable development patterns.