Ammoniacal nitrogen make up the frequent contaminant of surface and groundwater, exceeding appropriates standards around landfills in Malaysia. Leachate and groundwater samples were collected from an ex-landfill site at Taman Beringin in Kuala Lumpur, Malaysia and were tested for Various physico-chemical parameters to investigate the characteristics of the groundwater and possible impacts on the environment. The results showed considerable impact of leachates on groundwater with high concentration of most chemical parameters in groundwater samples. COD (101.75±99.42), BOD (28±30.99), NH-N (31.10±19.12), F-(0.72±0.32) and heavy metal; Pb (0.042±0.045), Ni (0.016±0.006), Fe (0.41±0.68) were above the Malaysian National Drinking Water Quality Standard (NDWQS) and National Water Quality Standards (NWQS) CLASSII A. In particular, the levels of NH3-N recorded in all the groundwater wells investigated at BH3 (12.89), BH5 (22.22), BH6 (32.01) and BH7 (57.30) were far above the NWQS CLASS IIA set at 0.3mg/L. Remedial measures are suggested to minimize the effects on the environment; improving the quality of the leachates and prevent further spreading of leachates into river, drinking water wells and other groundwater resources via groundwater flow are recommended.