When the war ended in November 1919, Mann accepted a job as the assistant editor of the USDA's Bureau of Entomology.

Mann left Washington, D.C. in 1922 and moved to New York City, where she became a junior editor at The Woman's Home Companion.

[2] Mann accompanied her husband on fact-finding trips to other zoos and field work expeditions around the world, including to Argentina, British Guiana, Liberia, and the East Indies.

[5] On one trip to Indonesia, they brought 900 animals (many of which found homes at the Maryland Zoo) back to Washington, D.C.[6] Together, Lucile and William Mann traveled to countries on nearly every continent.

From 1956 until her retirement in 1971, Mann was zoo editor, responsible for writing the Annual Report and other publications for the National Zoological Park.