Shi Hyun Ahn turned pro in 2002 and played mostly on the 'Dream Tour', the Korean equivalent of the Futures Tour. She ended up leading that tour at the end of the year, so in 2003 she qualified to play on the KLPGA tour full time.

She was in fourth place on the KLPGA money list and thus was invited to play the CJ 9 Bridges Classic, an LPGA event that takes place in Korea. She shocked almost everyone by not only winning that event, but by leading it from start to finish and beating Se Ri Pak when the two were paired together in the final group. Her win there was the first on the LPGA tour by a non-LPGA player in 8 years. She was also the sixth youngest to win on the tour in history, at just over 19 years of age, and the youngest international player to win in history.

The win earned her two years of status on the LPGA tour: non-exempt status in 2004 and exempt status in 2005. It also earned her a chance to compete in the Tournament of Champions in 2003, where the defending champion was once again Se Ri Pak.

Shi Hyun has become a big celebrity in Korea. Her fan club exploded from just 50 members before the 9 Bridges to over 6,000 just after it. She is frequently featured in newspaper articles, where she is invariably called 'Cinderella' Shi Hyun Ahn.

Shi Hyun's schedule was definitely accelerated in the wake of her winning the CJ 9 Bridges Classic. Originally, she had planned to hone her game in Korea for a few years, in the process learning a bit of English and preparing herself mentally for the Big Leagues in America. Now, suddenly, she found herself with just a few months to prepare for the LPGA tour. She made the most of this time, working intensely in order to make the biggest splash possible. And she did! In her first two events of 2004, she managed two top five finishes. Shortly thereafter, however, Aree Song, the player most people considered a shoo-in for Rookie of the Year, nearly won the Nabisco Championship, and it looked as though Shi Hyun might fade a bit (she missed the cut at that event).

But Ahn was far from done. At the year's second Major, she made an enormous run at Annika Sorenstam in the final round. Coming from a huge distance back, she came to as close as two shots out of the lead before Annika gathered herself and put it away. Still, Shi Hyun's second place finish was a great achievement, and put her back into the Rookie race.

Shi Hyun managed one more second place finish later in the year, and though she ran out of gas a little bit towards the very end of the year, her great play allowed her to capture the Rookie of the Year award from Song. She was the fourth Korean in seven years to be so honored.

2005 proved to be a bit of a down year after the high of 2004. However, she still managed six top tens and finished in the top 40 on the money list. In 2006, she rebounded nicely. In the early part of the season, she made herself a factor at several important tournaments, notably the LPGA Championship, where she had a chance to get into the playoff with Karrie Webb and Se Ri Pak, but hit her approach on the final hole into the water. She also contended at the US Women's Open, and played well at the Wegman's LPGA, where she led after two rounds but faded. She struggled with back injuries, which forced her to miss a large chunk of the season.

Ahn had a decent 2007 season without too many injury issues, at least none that were publicized. She wound up finishing 27th on the money list, and played in both the Kyoraku and Lexus Cups at the end of the year.