She starred in television series Yellow Handkerchief and Terms of Endearment early in her career, and became a sought-after model in commercials. Her projects in 2012 were hugely successful, with her period drama Moon Embracing the Sun topping the TV ratings chart, and her film Architecture 101 becoming a box office hit. As a high school student, Han Ga-in appeared on a TV quiz show and was also captured in footage of interviews with other students.
Entertainment bigwigs spotted her in the news clip and immediately went to her school to offer her a part. She debuted in an Asiana Airlines commercial in 2002, and was cast in the KBS2 drama Sunshine Hunting. KBS Drama Awards named her best new actress in 2003 for Yellow Handkerchief, and best actress for Terms of Endearment in 2004.
She soon became one of the most sought-after faces in the TV commercial industry. But despite her early success, Han struggled to overcome her image as strictly a pretty face rather than a serious actress. Over the past decade of drama appearances, the popular actress repeatedly played familiar characters and her performances failed to wow audiences.
After Witch Yoo Hee wrapped in 2007, Han publicly criticized the director and writers for the drama's poor quality. She went on a three-year hiatus afterwards, merely starring in advertisements. Categorized as a "CF star," Han wanted to change that misconception with her comeback in 2010.
In Bad Guy, she attempted to transform her image as a pure and innocent girl to a materialistic woman who dreams of climbing the social ladder. 2012 was the most successful year of Han's career yet. Period drama Moon Embracing the Sun, in which she played the heroine, an amnesiac noblewoman-turned-shaman, ended with an audience share of 40 percent when the final episode aired.
Then her film Architecture 101 got rave reviews and set a new box-office record as the highest-grossing Korean melodrama. She considers her character in the latter as the closest to her real-life personality. She was managed by J. One Plus Entertainment from 2009 to 2011, and when her contract expired, she signed with Lee Byung-hun's agency BH Entertainment in December 2012.