Joo was born on October 11, 1990. She has spent her childhood in Indonesia because her father worked in Indonesia before. She was one of the contestants in 'Superstar Survival' alongside with 2PM's Chansung, Taecyeon and Junho on 2006 where Junho was the winner. Although she didn't make it, she got accepted to be a trainee at JYP. She is currently attending Dongguk University in Division of Theater. She has a younger brother Jung Ilhoon, who also is a singer/rapper that debuted in a seven-member male vocal group BtoB under Cube Entertainment in 2012.
On January 10, 2008, JYP Entertainment stated that they will have a new solo singer, Joo. She made her debut stage on January 11, 2008 with her single Young Girl in KBS Music Bank. Although Joo has made her debut, she thought that she was not ready yet, so she trained for another 2 years before making her comeback in 2011.
On January 3, 2011, Joo finally release a video in her Official YouTube with her single 'Bad Guy' where 2PM's maknae Chansung was featured alongside. The single is part of her album called 'Heartmade'. On January 7, 2011, she made her comeback stage on KBS Music Bank with her single 'Bad Guy' On May 2011, Joo released a teaser with Super Junior's Leeteuk with a song called 'Ice Cream'. The song gives off a very happy feeling as the two singers enjoy each other's company. With the set and clothes being mostly white, it will be a cute and bright music video. On May 16, 2011, Joo and Leeteuk released 'Ice Cream' video on her Official YouTube. On May 23, 2011, JYP Entertainment officially announced that the artists of JYP will come together for two “JYP NATION in Japan 2011” concerts in August. The star studded line-up includes Park Jin Young, Lim Jeong Hee, Wonder Girls, Joo, 2AM, 2PM, miss A, and San E. The two concerts are scheduled for August 17 and 18 at the Saitama Super Arena, and tickets will go on sale June 1 at the Hottest Japan mobile site. On October 10, 2011, JYP Entertainment announced that Joo has been selected as a leading actress in a musical.
JYPE reported that "JOO was cast as the leading actress in a musical 'Youthful March’ scheduled from November 12 to January 29, 2012." Joo will be on a musical stage for the first time and said, “I excited with my debut in the musical world. I know this is my just starting and I play a leading role so I’ll practice hard for the performance to make a good work. And I’ll push myself to present a more gorgeous and newer appearance than before as a musical actress, not a singer. I appreciate if you cheer me up.”