She made an immediate impact, winning the Louise Suggs Rolex Rookie of the Year award on the strength of four top-20 finishes - the first non-exempt player to win the honour since Lisa Hackney (Hall) in 1997. She has remained extremely consistent ever since, and despite losing ground during 2007, when she gave birth to her first child, she bounced back in 2008 with nine top-10 finishes, ending the year a very respectable 18th in the Rolex World Ranking. However, because of her inactivity, she was not available for the 2008 HSBC Women's Champions.
In 2008, Han recorded nine top-10 finishes, including ties for third at both the Wegmans LPGA ans Hana Bank KOLON Championship 2008; carded a career-low 61 in the third round of the LPGA State Farm Classic, which set a LPGA record for the lowest third-round score; crossed the $5 million mark in career earnings at the Ginn OPEN, where she finished tied for 13th; carded her second LPGA career hole-in-one at the Kraft Nabisco Championship.
In 2009, Han’s best finish was a tie for third at the RICOH Women's British Open, her career-best finish at a major championship, and crossed the $6 million mark in career earnings; also tied for third at the LPGA State Farm Classic.
In 2010, Hee Won Han's best performance of the year was when she finished tied for fourth at the ShopRite LPGA Classic.
In 2011 Hee-Won Han finished tied for sixth at the CN Canadian Women's Open; tied for 25th at the Wegmans LPGA Championship; tied for 35th at the Honda LPGA Thailand; tied for 40th at the HSBC Women's Champions.
During the 2012 LPGA season Han made 21 cuts from 25 tournaments and finished T-5 at the ShopRite LPGA Classic .