This chapter focuses on manifestations of informality in Nairobi’s tenement housing, rather than its slums. We chose to focus on informal tenement housing because it gives us the opportunity to explore another aspect of informal urbanization, whereby informality is understood as a dynamic process which occupies a fluid space between legality and illegality. One similarity between informal settlements and sub-standard tenement housing is that they offer affordable accommodation and access to urban opportunities to citizens. In both cases, however, this housing is often available in dense, overcrowded conditions, lacking in basic services and infrastructure. Socio-politically, they embody the unequal power relations between newly arrived migrants (tenants) and landlords, within an environment of tacit neglect by the State. This attitude encourages further exploitation and neglect that nurtures feelings of disenfranchisement and uncertainty among tenants. The chapter unpacks these issues, beginning by framing a brief theoretical background. It then proceeds to map the social, political, and economic environments within which tenements are produced in Nairobi, before exploring a case study to illustrate and discuss these issues. We then conclude with a reflection on the implications of tenement’s informality on local and global understandings of urban informality. The chapter demonstrates that tenements feature varied aspects of urban informality that pose simultaneous benefits and challenges for tenants and necessitate further attention from policy and researchers.