Search for larvicidal active compound(s) is one of the several attempts to find effective, affordable and safe ways to control mosquito. The aim of this study is to investigate the toxic effect of Azadirachta indica leaves aqueous extract against mosquito’s larvae under laboratory conditions. Objectives to aim of this study is to active compound sensitivity and toxic of mosquito larva to water extract of Azadiracta indica (Neem). Experimental study to find out the toxic effect of aqueous extract of Neem tree Azadiracta indica on mosquito larvae was done. Aqueous extract from leaves powdered and strained was used as stock solution. Serial concentration of 4.5% up to 18% was tested on mosquito larvae. The larvae were subjected to the extract for 24hrs.After that the toxic index was compared to Abate (temephos). The mortality rate was found to be ranging between 13% and 87%.Three trails were made and the average was taken. The LCD50 andLC90 were found to be 13.18% and 33.88% consecutively. The toxic index compared to Abate (temephos) was found to be 0.02(2%). Separation and standardization of the active ingredient was recommended to bring a solid lethal effect. There was heterogenetic in the larvae population which may mean that resistant to aqueous extract could develop.