In September 2009, TS Entertainment announced that they will be debuting a four member girl group in October 2009. Hana debuted with the stage name of Zinger, along with Han Sunhwa, Song Jieun and Jun Hyoseong, as the group, Secret. Prior to their debut, the group was on a documentary show called "Secret Story" which chronicled their debut process. They released their debut single "I Want You Back" in October 2009.
In April 2010, Secret released their first mini album entitled Secret Time which spawned them the hit single "Magic" and served as their breakthrough song in South Korea. In August 2010, they released their second mini album entitled "Madonna" and the title track continued their success as it topped the Gaon Single Charts.
In January 2011, the group deviated from their "sexy" and "sassy" image and released Shy Boy, a "cutesy" and retro inspired song. Although they were worried with the 180 degrees transformation, the single exceeded their expectations as the song was a huge success. Shy Boy charted strongly in digital charts and Secret won their first trophy on music shows with the song. They won a total of 5 trophies in various music shows with Shy Boy. Secret continued their success with the release of their second CD single entitled "Starlight Moonlight". The title track became another hit for Secret as the song reached number one on the Gaon Monthly Singles Charts and won them another trophy in SBS's Inkigayo.
The same year, Secret began a foray of Japanese activities with the release of Madonna and Shy Boy (EP). The Japanese remake of "Madonna" debuted at number nine in the Oricon singles charts. Secret was one of the first three Korean girl groups to debut on the Oricon chart in the top 10, the others being Kara and Girls Generation being the first and second respectively. In October 2011, released their first studio album entitled "Moving in Secret" and spawned them another hit with the lead single "Love is Move. She also participated in the production of Moving in Secret by writing most of the rap parts in their songs and the album featured a solo track for Hana entitled "Amazinger". Secret released their first mini album in Japan entitled Shy Boy (EP). The mini album debuted also at number nine on the Oricon album charts.
In February 2012, Secret released their second CD single in Japan entitled "So Much For Goodbye".
Starting from promotions for Secret's single "YooHoo" from their album Letter from Secret released April 30, 2013, Hana began officially promoting under her real name, Jung Hana.
Hana is an only child. Her mother was a singer who had passed the TBS Talent Exam and released a single in South Korea. Her father is a martial artist and was a presidential bodyguard. She is also friends with 2NE1's CL and Wonder Girls' Sunye while attending the same dance academy in middle school.
On the 11th of December, 2012, at 2am, Hana was involved in a car accident with the other Secret members, breaking her ribs and bruising one of her lungs. A van that had been carrying her and the other members slipped off the road and turned over on itself. The incident was followed by harsh Tweets directed at Hana. Hana tweeted on the 13th,
“After collecting my mind and reading the news, I started looking at all the comments. [The replies are too much.] I’m asking you to think about whether you could post those words if it was your family member or someone you love who was in the same position. Though my body and strength are weak, it’s getting hard for my heart too.”
The girls decided to rest until the 28th of December, despite releasing their newest single, Talk That on the 4th.