The 1988 United States Senate election in Washington was held on November 8, 1988. Incumbent Republican U.S. Senator Daniel J. Evans decided to retire instead of running for re-election to a full term, after being appointed to the seat in 1983, and won re-election to a partial term that same year. Republican former U.S. Senator Slade Gorton, who had just lost a re-election bid in 1986, won the open seat.