Insomnia symptoms are highly prevalent among the elderly. Nearly half of the elderly population reported difficulty in initiation and maintaining sleep. The presence of insomnia affects the quality of life of elderly and increases the risk of falls. This study aims to measure the prevalence of insomnia among a group of elderly living in geriatric homes in Cairo and to assess the factors affecting it. A cross sectional study was conducted on 184 elderly living in two geriatric homes in Cairo. Athens insomnia scale was used to assess insomnia through an interview questionnaire. The prevalence of insomnia among the studied elderly in geriatric homes in Cairo was 36.4%. Higher prevalence of insomnia was found among males and married elderly. Also, insomnia was associated with longer stay in geriatric homes. Feeling sleepy during the day (59.2%) was the most prevalent symptom. Suffering pain (73.5%), nocturia (42.7%), and suffering from chronic diseases (40.4%) were significantly associated with insomnia. A significantly higher percentage of elderly with bad self-perception of owns health, suffered of insomnia (77.8%). This study reveals that changes in lifestyle, optimization of living environment and symptom control can reduce the burden of insomnia and improve quality of life of institutionalized elderly in Egypt.