Olaru was a successful junior player. She was the runner–up in both junior singles and doubles at the 2005 French Open, and captured the 2006 US Open doubles title along with Mihaela Buzărnescu. Her best professional Grand Slam result so far has been the third round of the 2007 French Open, when she defeated the 30th seed Julia Vakulenko in straight sets and lost to eventual runner–up, the seventh seed Ana Ivanovic. Olaru reached her highest singles ranking, world No. 53, on 27 July 2009, and her best doubles ranking, No. 32, on 28 August 2017.