The 47-year-old Barrett defeated Democrat Jane Ballard Dyer, a 50-year-old former Air Force pilot who now flies for FedEx.
Barrett is the second-ranking Republican on the Budget Committee. He was the lone South Carolina U.S. House member to vote against the $700 billion bailout bill on its first pass earlier this year. He voted for the bill when it came back to the House with changes.
It will be Barrett's fourth term in the U.S. House.
South Carolina's 3rd Congressional District runs along the Savannah River in the northwestern corner of the state.