We examine the patterns and determinants of household transitions into and out of poverty among the urban poor in two Nairobi informal settlements in Kenya between 2006 and 2009. We find worsening household poverty over time, with the proportion of poor households increasing from 51.2 percent in 2006 to 54.9 percent by the end of 2009. Over the period, 34.5 percent of households remained in chronic poverty, 20.4 percent fell into poverty, 16.7 percent successfully escaped poverty and 28.4 percent fully remained out of poverty. We identify slum of residence, gender and marital status of household head, attainment of at least secondary education by household head, consistent engagement in formal employment, household size and the incidence of births within a household, among key determinants of household poverty transitions. Our results underscore the need for anti-poverty policy options around provision of economic opportunities, addressing disadvantages of female-headed households, promoting access to at least secondary education, smaller household norms and birth control among the urban poor. While the outcomes are consistent with some national trends, the need for the design and implementation of slum and sub-group specific anti-poverty policies are significantly evident. Ã