Championships in Ponte Vedra Beach, Stosur was eliminated in the first round by second seed and eventual champion, Caroline Wozniacki. She then played for the Australian Fed Cup team in Mildura. Australia against Switzerland in their World Group II playoff. Stosur won the opening rubber of the tie in straight sets, then sealed the victory for Australia in the third rubber with a tight three-set victory, improving her 2009 Fed Cup singles record to 6–0. With this result, the Australian team advanced to the World Group II in 2010. In the clay-court season, Stosur was eliminated in the first round of the Rome Masters by qualifier Yaroslava Shvedova, and was also defeated in her first match in doubles. She then competed at the Madrid Masters, where she upset tenth seed Agnieszka Radwańska in the first round, but fell to Anna Chakvetadze in the second. Stosur and Stubbs made it to the semifinals, but were defeated by the world-No.-1 team of Black and Huber. At the French Open, they fell in the third round to 16th seeds Yan Zi and Zheng Jie. In singles, Stosur defeated Francesca Schiavone in the first round and Yanina Wickmayer in the second. She then beat fourth seed Elena Dementieva in the third round and Virginie Razzano of France for a place in the quarterfinals, where she defeated Sorana Cîrstea and advanced to her first Grand Slam semifinal against seventh seed and eventual champion Svetlana Kuznetsova. After losing the first set, Stosur fought back a break of serve to win the second set in a tiebreak, but lost in the final set. This made her the lowest-ranked seed in the tournament to reach the furthest. With this result, Stosur cracked the top 20 for the first time in her career. Stosur started the grass-court season playing at the Eastbourne International. She defeated Sabine Lisicki in the first round, before losing in the second round to sixth seed and eventual champion Wozniacki. Having beaten Black and Huber in the semifinals, she was a runner-up in the doubles tournament, losing the final to Ai Sugiyama and Akgul Amanmuradova with Stubbs. As the 18th seed at Wimbledon, Stosur defeated Bethanie Mattek-Sands and Tatjana Maria (then Tatjana Malek), before losing in the third round to 13th seed Ana Ivanovic. In ladies' doubles, Stosur reached her second consecutive final, this time partnering Stubbs. The third seeds beat second seeds Anabel Medina