This study – an assessment of vulnerability of urban informal settlements to environmental hazards – was conducted in Korogocho as a response to the emerging world view that recognizes urban informal settlements as areas exposed to numerous environmental hazards and disasters. This is particularly evident in Kenya where the issue of proliferation of informal settlements and urban sprawl has been on the rise. The study used both primary and secondary sources of data to achieve its objectives. The study employed the use of community-based indicators system (Bollin 2003) for vulnerability assessment at a micro scale level. The indicators were weighted depending on the hazards, exposure and vulnerability, and coping capacity. The study results revealed that Korogocho is highly vulnerable to disease related hazards, floods, fires and droughts which culminate in famine and general insecurity. The lack of a cogent land-use plan for the area further complicates the problem. The findings from this study would go a long way in building disaster resilient cities in Africa.