In 1950, Devereux was elected as a Republican to the U.S. Congress for Maryland's 2nd Congressional District by defeating incumbent Democratic Rep. William P. Bolton. Devereux would serve four terms in the U.S. House of Representatives from January 3, 1951, to January 3, 1959. During his Congressional career, he supported public school desegregation and ending racial discrimination in employment. He served on the House Armed Services Committee from July 3, 1952 (replacing John Anderson (R-Calif.)) until he left Congress. Devereaux did not sign the 1956 Southern Manifesto and voted in favor of the Civil Rights Act of 1957. He was not a candidate for renomination in 1958, but was an unsuccessful candidate for election as Governor of Maryland against Democrat J. Millard Tawes from Crisfield on Maryland's lower Eastern Shore of the Chesapeake Bay. In 1960, he was named Republican Party chairman in his congressional district.