Informal urbanism has been generally studied within social, economic and political frameworks, yet little is known of how it performs in terms of urban vitality. The aim of this article is to better understand the urban vitality of informal settlements and how they can be improved by using a combined morphological approach that encompasses street-network accessibility, building density, land use diversity and transformability index. This study focuses on the city of Cairo, which has experienced rapid urban growth over the last seven decades. Much of this growth has concentrated in informal settlements on the outskirts of the metropolis. Taking Manshiet Nasser district as a case, we measured the degree of urban vitality of the area through a combination of Space Syntax, Spacematrix, and the Mixed Use Index (MXI). Informed by a transformability index (TI), the results can be used as part of the design process to (re)develop unattractive areas. The findings show that this combined approach works as a diagnostic tool for detecting development potential and, therefore, underpins the identification of cost-effective ways of intervention, for enhancing vibrant urban environments.