Food insecurity is recognized as an increasing problem worldwide and a critical factor for the economic growth and development of a nation. This study investigated socio-economic effects of food insecurity among urban poor households in Kamukunji slums, Eldoret Municipality, Kenya. The main objective is to determine the causes of household food insecurity and assess their socio-economic effects. A total of 303 households were targeted and selection done using stratified random sampling. The study utilized both primary and secondary methods of data collection. Primary sources were: non-participant observation, structured questionnaires and key informant interviews. The findings show food insecurity was a result of poverty, lack of a stable income and high food prices. The effects of food insecurity include: skipping meals, school dropouts, purchase street food and poor wages, malnutrition and stunted growth. Adaptation strategies of residents to food insecurity include: early marriages, eating less preferred food, engaging in prostitution and sending children on streets to beg. The study recommends educating residents to improve household food security.