Depression among elderly is emerging as an important public health issue in developing countries like India. Published evidence regarding the magnitude and determinants of depression among elderly hailing from urban slum is currently limited. Hence, the current study was conducted to assess magnitude of the problem and identify factors associated with depression among the elderly in an urban slum. A cross-sectional study was done to cover total of473 elderly persons from an urban slum in Bangalore, India. They were assessed for depression using Center for Epidemiologic Studies Depression scale. The overall prevalence of depression was found to be 37.8 (95 % CI= 33. 43-42.16). Multivariate analysis revealed that unemployment (self or children) (odds ratio (OR) 2.6; 95 % confidence interval (CI) 1.41-4.72), illness of self (OR 2.2; 95 % CI 1.45-3.21), female gender (OR 1.9; 95 % CI 1.19-2.89), conflicts in family (OR 1.6; 95 % CI 1.03-2.43), and marriage of children or grandchildren (OR 1.6; 95 % CI 1.02-2.68) as independent risk factors. Depression among elderly is an important health issue of this area. Psychological intervention need to be provided for all elderly persons especially at the time of being diagnosed with any kind of illness. Strategies should be targeted to the females. The stressful life events need to be identified and remedial actions taken. This facility should be made available to them at the primary level of health care. There is a need to include screening of depression in our national health programs.