Abstract: Mosquito transmitted infections are the leading cause of morbidity and mortality in many African countries including Uganda. The mosquitoes lay their eggs in stagnant water. The eggs then hatch into larvae, pupa and later into adults. Synthetic insecticides are commonly used to control these deadly insects. However, most of these insecticides are very expensive and non-environmentally friendly. There is also increased resistance of mosquitoes to these insecticides hence the need to search for new sources of bioactive compounds that can potentially deplete and incapacitate mosquito populations. Jatropha curcas has been reported to contain larvicidal, insecticidal and insect repellency properties. This study therefore aimed at assessing the larvicidal activity of aqueous extracts from Jatropha curcas seeds, leaves, barks and roots on mosquito larvae in vitro using a Completely Randomized Experimental Design. The seed extract exhibited a mortality rate of 83.3% at 80% concentration level and 80, 60, 56.7 and 40% mortality rates at 60, 40, 20 and 10% concentration levels, respectively. The leaf extract exhibited a mortality rate of 43.3% at 80% concentration level and33.3, 23.3, 13.3 and 10% mortality rates at 60, 40, 20 and 10% concentration levels, respectively. The bark extract exhibited a mortality rate of 43.3% at 80% concentration level and 26.7, 20, 13.3 and 6.7% mortality rates at 60, 40, 20 and 10% concentration levels, respectively while the root extract exhibited a mortality rate of 43.3% at 80% concentration level and 23.3, 20, 13.3 and 6.7% mortality rates at 60, 40, 20 and 10% concentration levels, respectively. In the control experiments, no mortality of mosquito larvae was noted. All the aqueous Jatropha curcas extracts were able to cause mortality of mosquito larvae within a period of 24 h. The mortality rates generally increased with increase in concentration levels of the extracts. However, apart from the bark extract, increase in the concentration levels of the rest of the extracts did not yield any significant difference in the mortality rates of the mosquito larvae at 5% significance level. Generally, the seed extract exhibited the highest larvicidal activity hence it could be used in the development of affordable, effective and environmentally friendly mosquito larvicides.