Larvicides are crucial for the control of mosquito related diseases. The need to use pesticides derived from plants has received increased interest as an inexpensive technology compared to the high cost of the traditional synthetic compounds for mosquito control in the endemic areas of poor nations of the world. The aim of this study was to find out the toxic effect of a water extract of Khaya grandifoliola “Mahogany” bark on mosquito larvae. The bark was powdered, soaked in water and strained. It was then used as a stock solution. Serial concentrations of 3% up to 27% were tested on mosquito larvae. The larvae were subjected to the extract for 24hrs. Four replicates were made and the average was taken. The mortality rate was found to be ranging between 13% and 100%. The LC50 and LC90 were found to be 0.6% and 0.9% consecutively. The toxicity index compared to Abate (temephos) was found to be 0.45(45%). Because of the impacts of traditional insecticides on other aquatic fauna and the environment, quest for safer pesticides has attracted researchers to look into plants with pesticidal properties. Khaya grandifoliola “Mahogany” proved to be one of those plants. The aqueous extract of this tree has been found to be potent in controlling mosquito larvae. It is recommended to do more research on the water and other solvents extracts of the tree bark and may be other parts. Yet, since the chemical contents of plants generally depend on soil composition, it is of paramount importance to test extracts of “Mahogany” from different geographical areas.