She made her television debut in 2004 while participating in SBS' Superstar Survival as a finalist,[5] and in 2009, she was a regular cast on a variety show called Invincible Youth.

Teacher Sung Yong-ho, in charge of the school choir, helped Han by giving her chances to participate in competitions; then, she was admitted to Baekjae Art College.

[12] A few days before the college entrance ceremony, she got a call from an agent who watched Superstar Survival and became a trainee in TS Entertainment.

[15] In April 2010, they released their first mini album entitled Secret Time which spawned the hit single "Magic" and served as their breakthrough song in South Korea.

[19] On December 28, 2010, Han made a cameo appearance on MBC's daily sitcom, All My Love, playing Gain's old college friend.

[23][24][25][26] CNN International Seoul listed Han as one of the nine rising "it" stars in Korean entertainment citing her as a "multi-tasking" artist.

[40] In 2020, Sun-hwa was cast in the romantic-comedy drama, Backstreet Rookie, alongside Ji Chang-wook and Kim Yoo-jung, based on a webtoon of the same name.

She played Dae-hyun's (Ji Chang-wook) girlfriend and former boss, also a convenience store headquarters Public Relations team leader.

[45] In 2024, Han was cast as the female lead for the JTBC drama My Sweet Mobster alongside actors Uhm Tae-goo and Kwon Yul.

"White paper", or "baekji" in Korean, is a term coined by netizens and the cast of Invincible Youth, which is an English equivalent of the "dumb blonde" persona portrayed by Han in that show.

[27][49] She played a huge role in increasing Secret's popularity through Invincible Youth and other variety shows because of her dumb blonde persona.

[citation needed] In February 2015, Han signed a deal with popular handbag brand St Scott London as their exclusive model for Spring/Summer 2015 collection.

[53][better source needed] In August 2015, it was announced that Han, along with Super Junior's Choi Siwon, would be the honorary ambassador of the 11th Jecheon International Music & Film Festival (JIMFF).

Along with Jun Hyo-seong, B.A.P's Kim Him-chan and Bang Yong-guk, Han was chosen as a model for Kellan sportswear 11/12 Winter Collection in September 2011.