Against the backdrop of urbanization, cities have evolved globally, but more so in Sub-Saharan Africa (SSA) in recent decades. Cities in the sub-region differ in many ways from those in other parts of world. One of the major differences is the overwhelmingly informal nature of urban growth in many cities in SSA, a feature that has regulation and spatial pattern dimensions. These dimensions are, however, less explored in urban modelling research. Cities have not evolved alone, but, alongside with massive evolution in the methods of their abstraction. Cellular Automata (CA) and Agent-Based Modelling (ABM) are two popular techniques that have emerged from this evolution. These models are rarely applied to cities in SSA. After a period of independent applications, there is an increasing recognition that the two approaches are mutually reinforcing, hence are mostly integrated in recent urban growth models. Existing integrated ABM and CA models of urban growth hardly account for the predominantly informal dynamics (unplanned and unregulated growth) that characterise many cities in Sub-Saharan Africa. Following the above, this research pursues three main objectives: one, simulates the urban growth of a predominantly informal Sub-Saharan African city-region with urban CA; two, examines the evolving urban spatial structure of Sub-Saharan African cities and the relationship with mainstream urban spatial structure models; and, three, develops an integrated ABM and CA model that simulates urban residential growth of a predominantly informal city-region in SSA. In exploring the first objective, diverse spatially explicit datasets are drawn from Accra, and SLEUTH, a dynamic urban CA model, is applied to the Ghanaian city-region. In relation to the second objective, the research draws on wide ranging spatial datasets and combines SLEUTH with urban spatial metrics to analyse the evolving spatial structure of Kumasi city-region (Ashanti region) of Ghana. The third, also the overarching objective, develops TI-City model (The Informal City model), an integrated ABM and CA model for simulating urban residential growth of predominantly informal cities in SSA. The model, which relies on spatial and empirical socio-economic datasets in its development, is applied to Accra city-region The research finds urban growth in both Accra and Kumasi city-region to be highly spontaneous and rapid; and new developments fast turn into urban growth nuclei. It also uncovers that, while Kumasi 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. The application of TI-City, the model newly developed by this research, to Accra city-region shows that the model can offer unique insights into the dynamics of urban residential growth in predominantly informal SSA cities. TI-City could, therefore, function as a decision support tool in Ghana and many Sub-Saharan African countries. The research further discusses the implications of the model for theory, urban policy and practice.