A majority of urban residents in sub-Saharan Africa (SSA) and other developing regions live in informal settlements, or slums. Much of the discourse on slum health centres on younger generations, while an intensifying agenda on healthy ageing as yet lacks a systematic focus on slums. Similarly, the global age-friendly cities (AFC) movement does not, thus far, extend to slums. This paper examines the particular challenges that a slum-focused age-friendly initiative in SSA may need to address, and the relevance of present AFC indicators and domains for initiatives to advance the health and well-being of older slum dwellers. The analysis builds on the case of two slum communities in Nairobi, Kenya. It analyzes two bodies of relevant evidence from these settlements, namely on the health and social circumstances of older residents, and on the local application and measurement of AFC indicators. The findings point to a set of unsurprising, but also less obvious, core health and social adversities that an age-friendly initiative in such settlements would need to consider. The findings show, further, that the current AFC domains and indicators framework only partly capture these adversities, but that there is potential for adapting the framework to be meaningful for slum settings. The paper concludes by underscoring the need for, and opportunities inherent in, the pursuit of an “age-friendly slums” initiative going forward.