The problem of urban food insecurity in Ethiopia has received little attention despite its increasing importance and far reaching ramifications. High rates of unemployment resulted from sluggish economic growth and low level of investment in urban centers combined with high population growth has negatively affected income earning potentials of the residents. Urban population will continue to grow with its associated problems unless meaningful development interventions backed by research findings are undertaken. Since research findings on factors affecting food insecurity in urban areas are scarce, this research, in particular, fills this research gap. The present study attempts to examine the food insecurity situation, estimate food insecurity gap and severity and identify the determinants of food insecurity in Addis Ababa city at household level. The primary data source for this work was the Addis Ababa urban household socio-economic data collected by undertaking a survey on 140 households. Three stage cluster random sampling technique with proportional to size was used to select respondents from the study area. Data were analyzed by using descriptive statistics such us mean, standard error, frequency, and percentage. Econometric analysis was used to identify the determinants of food insecurity, and Foster-Greer-Thorbecke model indices were employed to estimate the food insecurity gap and the severity of food insecurity. The descriptive statistics revealed a significant mean difference (p<0.05) between the food secure and food insecure households in terms of household size, age of household vii head, ownership of bank account, household income, kilocalorie available per individual, remittance and gift received and daily food expenditure per adult equivalent but education level of household head was also statistically significant (p<0.01). A Tobit econometric model has identified six out of eleven variables included in the model as significant (p<0.05). Household size, household income, household head age , household head education, ownership of bank account and income from remittance and gift were found to be significant determinants of food insecurity in the study area. The head count ratio computed by FGT model revealed that 47 percent of sample households were food insecured. The food insecurity gap and severity were 16.83 and 6.9 percent, respectively.