In 2002, Yoona joined SM Entertainment Saturday Open Casting Audition, in which she sang WAX's "Please", danced Britney Spears' "Oops..! I did it again" and BoA's "Valenti". Later, she began to train under SM Entertainment with the other trainees in the areas of acting, singing and dancing. In 2007, Yoona was chosen as a member of the group Girls' Generation. The 9-member girl group debuted on August 5, 2007.
Yoona made her debut as an actress in 2007 with the drama Two Outs in the Ninth Inning. In 2008, Yoona acted in the drama Woman of Matchless Beauty before her first leading role in the daily drama You Are My Destiny which she won her important recognitions in acting. YoonA filmed her 2009 drama Cinderella Man (신데렐라맨) alongside with Kwon Sang-woo.
In 2012, Yoona was cast in a lead role with Jang Keun Suk in the drama entitled Love Rain. The drama began broadcasting on March 26, 2012 on KBS2. Love Rain is a fantasy drama about fate and how the offspring of a previous ill-fated couple who met in the 1970s, also manage to fall in love with each other.
In 2013, Yoona starred alongside with Lee Beom-soo in the romantic-comedy drama "Prime Minister & I". The drama began broadcasting on December 9, 2013 on KBS2, and was produced by SM C&C. Though receiving low ratings, it received very positive reviews for its writing and acting, especially from the leads Yoona and Lee Beom-soo.
In July 14, 2014, SM Entertainment announced that Yoona will make her big-screen debut by starring in the Korean-Chinese movie "Goodbye Ani" as the protagonist Ani. Production will begin within the second half of 2014.