During April and May 1940, "Ceres" was assigned to the Eastern Fleet and based at Singapore. She was used to patrol off the Dutch East Indies coast in opposition to Japanese naval forces. In June she was assigned to operate in the Indian Ocean and based at Colombo and later Bombay, where she escorted tanker convoys from the Persian Gulf to the British colony at Aden. She then spent several months off the east coast of Africa, based at Mombassa, Kenya. Whilst on patrol off the coast of Somaliland she evacuated troops and civilians from British Somaliland to Aden, and she was later involved in convoy duties sailing around Cape Horn between Durban and Cape Town. Later that year she was sent to the Seychelles and other islands to search for German commerce raiders, who were preying on Allied shipping in the area.