King teamed with Navratilova to win the women's doubles title at the US Open, King's fourth women's doubles title at that tournament and fourteenth Grand Slam women's doubles title overall. To end the year, King was undefeated in five doubles matches (four with Evert and one with Rosemary Casals) as the U.S. won the Federation Cup in Melbourne, Australia. She also teamed with Tracy Austin in the 1978 Wightman Cup against Great Britain, beating Anne Hobbs & Sue Mappin in the best of seven rubbers, despite the US losing the Cup 3–4. During the Federation Cup competition, King hinted at retirement from future major singles competitions and said that she was "sick and tired of continued surgery" in trying to get fit enough for those events. Nevertheless, King had foot surgery on December 22 in an attempt to regain mobility for a return to the tennis tour.