Born to a Roman Catholic family, he enlisted in the Ceylon Naval Volunteer Force (CNVF) as a Signalman/Gunner at the start of the World War II. In September 1943, Wickremasinghe was serving on board HMS Overdale Wyke as yeoman to the captain, when she intercepted and accepted the surrender of the Italian sloop Eritrea. He later served in the Burma campaign and was awarded the Burma Star. With the formation of the Royal Ceylon Navy in 1950, Wickremasinghe received a to a regular commission. As a Lieutenant Commander, he served as Commander Northern Area from 1965 to 1966 and a Commander during the JVP Insurrection.