Baek began her music career in 1999, entering the South Korean dance scene with her first album Sorrow. The first single, "선택" (Choice), was unusual in that it was one of the first Korean pop songs to feature Latin beats. However, this single proved to be popular and charted very well. She quickly followed this album with a second, Rouge, which came out in April 2000, selling 360,000 copies, and cementing her status as one of South Korea's most popular female dance artists.

In 2000, a sex tape featuring Baek and her manager at the time, Kim Shi-won (alias Kim Seok-jin), was leaked onto the internet. The video had been recorded secretly in a hotel room without Baek's knowledge, and was later used to threaten Baek when she attempted to change her contracted manager at the peak of her career. The former manager, who fled to the U.S., is currently serving time in a Los Angeles jail for charges of sex with a minor, which he also recorded on video. The scandal nearly ruined Baek's career, leading to a five-year absence from the limelight from which she only emerged in 2006.

Two years after the release of Tres, Baek released her fourth album Smile in September 2003. Although not a runaway success, it managed to sell a decent number of copies, placing 46th for the year. However, her real comeback occurred in 2006, when Baek released her fifth album Smile Again in March. "사랑 안해" (I Won't Love), her first single from the album, was a ballad, unlike the rest of her Latin-style singles. Although this was a significant change, it proved to be a very popular song, getting to the top spot on certain performance show charts. This change was not a permanent one, as there were many Latin/dance tracks on the album. In fact, the second single has seen Baek going back to her musical roots, as Ez Do Dance is a sexy Latin number. She performed this single until the end of summer 2006, at which point she finished promotional activities for the album. In November 2006, Baek won Best Female Solo Singer at the MKMF Awards and was nominated for the Overseas Viewer Award.

On September 7, 2007 Baek's sixth album, The Sixth Miracle, was released, with the lead single "사랑 하나면 돼" (I Only Need One Love). She won an award for the album at the Seoul Music Awards in January 2008.

After recuperating from her surgery, Baek returned with her seventh album, Sensibility, released on November 14, 2008. It was reported that she would come back with a dance single to showcase her strengthened voice, but instead came back with "총 맞은 것처럼" (Like Being Hit by a Bullet), a mid-tempo ballad. The single hit #1 on various online music sites and hit #1 on KBS's music program Music Bank.

In 2009, after suffering from a high fever and dizziness from the flu and hypotension, Baek stopped a dinner concert midway. After singing her fifth song, she told the audience, "I am very sorry for being on stage despite being sick. I won't be able to continue my performance." Experts speculated that refunds cost Baek and her agency losses of nearly ₩200 million.

She collaborated with Mighty Mouth for their comeback single "사랑이 올까요" (Will Love Come), released on March 12, 2010 along with a music video. This is her second collaboration with the group; she was previously featured on their mini-album Love Class in the track Miss U, released on August 6, 2009. Her single Over Time topped various music charts on the day of its release on July 1, 2010, and Baek's greatest-hits album Timeless: The Best also sold very well.

Baek has also participated in numerous soundtracks for TV dramas, most of which have proven to be very popular, including Don't Forget for IRIS, Love Is Not a Crime for Ja Myung Go, Love and Love for Arang and the Magistrate, and Spring Rain for Gu Family Book. The most famous thus far has been That Woman from Secret Garden, which won Outstanding Korean Drama OST at the 2011 Seoul International Drama Awards. Baek said, "I love to participate in producing music for soaps if I like the female lead after reading the script. It's a thrill to hear my song played during melodramatic moments in soaps." She later released an album in 2013 titled Flash Back, a collection of the television drama soundtracks she recorded.

She and friend, singer Yuri, set up the successful online shopping Business IamYuri Mall. But Baek withdrew from associating with the brand in 2012, after the Fair Trade Commission fined several celebrity-run online shopping malls for posting faked user reviews.

Baek filed suit against a local plastic surgery clinic that had used her photo for online advertising without her permission. On June 24, 2013, the Seoul Central District Court found the clinic guilty of infringing on her rights for profit, and awarded Baek damages of ₩5 million (US$4,320).

The Actress was expected to give birth on May 24 but on May 22, Baek Ji Young’s management agency, Music Works, announced, “Baek Ji Young gave birth to her daughter.