Jooyeon debuted with After School's unofficial first appearance on December 29, 2008 at the SBS Song Festival, performing "Play Girlz" with Son Dambi. In the beginning on 2009, a few days before After School's debut, the group released their debut single, "AH!" alongside their EP, New Schoolgirl on 15 January'. On 17 January, she and After School made their live debut on MBC's, Music Core. She is a Vocalist and Visual in the group. Jooyeon was a famous ulzzang before debuting with After School. She was featured in Tony Ahn's Yutzpracachia and Taegoon's Betrayed music videos as well as various commercials. She made her acting debut with the drama, Smile Again (2010) and was a member of G7 in the variety show Invincible Youth. She is the leader of the Blue sub-unit. Appeared on MBC “Introduce Star’s Friend” as Son Dambi’s best friend in 2008. In 2012, Jooyeon had been a cameo cast in Korean dramas such as 'Salamander Guru', 'The Shadows' and 'Reply 1997'. She is also in Music and Lyrics 2 with actor Lee Tae Sung as a regular cast member. On November 21, 2012 The first Episode of Jeon Woo Chi aired which Jooyeon and fellow After school member UEE are casted in. The drama has 24 episode and Uee is the lead and Jooyeon is a supporting character. Jooyeon had her first CF for Japanese lingerie brand 'Maruko'
In 2011 Jooyeon Graduated from Dongduk Women's University with a major in broadcasting. She graduated on February 22. On November 21, Jooyeon was admitted to the hospital with acute nephritis. On November 29, she was discharged and had resumed all group activities.