Rapid urbanization, increasing prosperity, economic development coupled with changing lifestyle has produced a tremendous generation of waste in huge quantity. The dumping of this huge quantity of partially segregated waste has become a public health and environmental concern. According to an estimate, more than 9500 tons per day (TPD) of MSW (Municipal solid waste) is generated in Delhi and about 60% of waste is transported to these three-active landfills in order of maximum in Bhalswa followed by Ghazipur and Okhla landfill sites which are non-scientific landfill and less than 40% were transported to composting plant and waste to energy plant. These waste dump sites have finished their commissioned date and crossed the permissible height and come under matured landfill (old). Dumping of unsegregated waste in these landfills contribute long-term threat to groundwater as various parameter such as inorganic, organic and heavy metal liberate from leachate of unsegregated solid waste and concentration varies with season. Soil contamination, air pollution and various other environmental, health and social impacts in the vicinity of these landfills are found to be connected with uncontrolled dumping of waste. The study reported that, till date in Delhi, there is no single landfill which is controlled and provides with baseliner or proper cover. All three active landfill still received solid waste beyond their capacity without any attention to waste segregation. Impact of landfill leachate on groundwater revealed by presences of high concentration of various parameters like Chloride, Nitrate, Sulphate, Ammonium, Phenol, Iron, Zinc and Chemical oxygen demand in assessed which showed that quality of groundwater is significantly affected by the percolation of landfill leachate. The main problem of the landfill is the generation of toxic leachate and gases which finally end their life in groundwater and environment and ultimately reach to human and damage aquatic life present in water. On the other hand emission of greenhouse gases lead to the risk of fire and also cause global warming. Presently NGT had warned officer of these three landfills of Delhi to remediate landfill. There is an urgent need of leachate collection system and treatment facilities and gas trapping technologies at this landfill for energy generation and to protect the contamination of groundwater.