The crowning moment of Reid's career came in 1977, when she defeated fellow-Australian Dianne Fromholtz Balestrat 7-5, 6-2 in the final to win Australian Open women's singles title.

Reid also won the Australian Open women's doubles title twice (in 1968 and 1977), and the Wimbledon women's doubles title once (in 1978).

Reid was the women's singles runner-up at the Australian Open in 1970 (where she lost to Margaret Court in the final 6-1, 6-3), and at the US Open in 1972 (lost to Billie Jean King 6-3, 7-5 after beating Chris Evert in the semifinals 6-4, 6-2). In 1972, Reid reached the final of the inaugural WTA Tour Championships, where she lost 7-5, 6-4 to Chris Evert.

Reid was a member of the Australian team which won the Fed Cup in 1968. She also helped Australia reach four consecutive Fed Cup finals in 1976-1979. During that run, she beat several top players, including Rosie Casals (1976 final in Philadelphia 1-6, 6-3, 7-5), Virginia Wade (1977 semi-final on English grass 6-4, 6-4), and Tracy Austin (1978 final on Australian grass 6-3, 6-2).

Reid is arguably the best player of the Open Era, male or female, not to be inducted into the International Hall of Fame. Besides her 1977 Australian Open triumph, she won 26 further singles titles over the course of her career and reached an additional 40 finals. Reid was ranked in the world's top-10 for 12 consecutive years (1968-1979) and won at least one tournament annually from 1966 to 1979, except for 1975.

Reid began her international career in 1966 by reaching the semi-finals at both the Australian and the US Championships (in the latter she defeated defending champion Billie Jean King in the second round). In 1967, Reid again reached the semi-finals at the Australian Championships and also reached the sem-finals at the French Championships. She capped her last year on the professional tour in 1979 by beating Martina Navratilova for first time in tournament play (Family Circle Cup semi-final 6-3, 7-6, before losing to Austin in the final 6-7, 6-7) and competing in the season-ending WTA Tour Championships (limited to the year's top 8 players).

Reid was a member of the "Houston 9", the breakaway group led by Gladys Heldman in 1971 that formed the nucleus of the women's professional tennis tour. She also anchored a World Team Tennis team for each season of its inaugural incarnation (Boston Lobsters 1974-1976, and San Diego Friars 1977-1978). For the Friars in 1977, Reid was undefeated in singles against both Navratilova and Wade, beating each 3 times.

Reid married Grover "Raz" Reid, a Boston Lobsters teammate, in 1976. Raz retired as a player in 1977, and coached Kerry during the remaining three years of her playing career. The Reids then retired to South Carolina and raised two daughters.

Reid was made a Member of the British Empire by Queen Elizabeth II in 1979.