Borg and Simionescu in Snagov, Romania, on 24 July 1980
Simionescu won the French Junior Championships in 1974. She played on the WTA Tour from 1973 to 1980. Her best Grand Slam performance was reaching the fourth round at Wimbledon in 1977. She won one singles title and one doubles title. She reached a career-high singles ranking of world no. 36 in 1978.
Simionescu married Björn Borg on 24 July 1980, but the marriage ended in 1984. She never remarried, but lived together with former F1 racer J.-L. Schlesser for a few years, with whom she has a son (Anthony).