Derrick was a delegate to the Democratic National Convention in 1974. That same year, he was elected to the House from South Carolina's 3rd congressional district, succeeding longtime congressman William Jennings Bryan Dorn. He was reelected nine times. Although he represented a district that had become increasingly friendly to Republicans at the national level, he himself only faced serious opposition in 1988. Derrick served on the House Rules and Budget Committees during his tenure, and spent his final term as a Chief Deputy Whip.
Derrick did not run for reelection in 1994. As a measure of how Republican this district had become, one-term Republican state representative Lindsey Graham won the seat in a rout, taking 60 percent of the vote. By comparison, Derrick had won what would be his last election in 1992 with 61 percent of the vote. No Democrat has cleared the 40 percent barrier in the district since Derrick left office. This included 1996, when Graham defeated Debbie Dorn, William Jennings Bryan Dorn's daughter, with 60 percent of the vote to Dorn's 39 percent.
