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. 2008, however, was her worst season since joining the LPGA; she only finished 55th on the money list. She seemed to be struggling with injuries much of the time. When she was healthy, she still played at her old level. Her best finish was a tie for 6th at the LPGA Championship. She did even worse in 2009, finishing 59th on the money list, with slightly more than $200,000 in earnings.

In 2010, her slide continued. She finished 61st that year on the money list, and had no top tens all year. However, she is still easily maintaining playing privileges on tour, despite her decreased earnings.

Shi Hyun made less than $65,000 on the LPGA tour in 2011 and saw her status fall to category 11 for 2012. She also played in Korea, and it was here that the most interesting development of the year happened. During her appearance at the KLPGA's Hanwha Classic in September, her group was followed by "Marco", a popular Korean television personality originally from South America. The gossip mills started buzzing, and soon afterwards, Marco revealed that he and Ahn had been dating for a year and were wildly in love. In November they were married, and have become quite an 'It' couple over there.

In late April, 2012, just six months after they wed, the couple announced the birth of their first daughter, Grace. Shi Hyun took the entire year off from golf to take care of her. She did not return to action until late in 2013, when she accepted a sponsor's exemption to play at the KLPGA's ADT-CAPS Championship. Amazingly, despite having not played in about two years, she carded a top ten finish. She decided to get back into golf seriously, and played a full schedule on the KLPGA in 2014.

Meanwhile, her marriage hit some rough spots; the low point came when police were called to end a physical altercation at their house. Ahn divorced her husband sometime around late 2013/early 2014.

Ahn had a decent but unspectacular 2014 season. She finished 32nd on the money list with just two top tens during the year. Her best finish was a second place at the first event of 2014, the LotteMart. She also managed a 3rd place later in the season.

Ahn made 136 million won in 2015, which placed her 42nd on the KLPGA money list. She had three top tens, with her best finish a fifth place.

2016 was an amazing year for Shi Hyun Ahn, thanks to her performance at the most important event of the year on the KLPGA, the Korea Women's Open. She found herself battling head to head on Sunday with Sung Hyun Park, the top player on tour. Yet it was Ahn who emerged triumphant, winning by a single shot. It was her first win in 12 years, and the first since the birth of her daughter.

Ahn did not have another top ten in 2016, but she did make 315 million won, which placed her 16th on the money list.

Ahn had a weaker 2017 season. She made about 143 million won and finished 45th on the money list. Her best finish was a 2nd place at the Samchully Together Open. Her 2018 was even more of a struggle. She finished 77th on the money list, with her best finish a 14th.

2019 was another weak season for Ahn. She finished 82nd on the money list with about 59 million won earned. On the plus side, she played the Evian, where she made the cut, finishing tied for 67th. Her best KLPGA finish was a tie for 29th.

In 2020, the whole world struggled with the Covid19 pandemic, which resulted in mass cancelations of events on all golf tours. When action started up in Korea in mid-May, Ahn played a full schedule, but did not have great results. Her best finish was a 20th, and she ended up earning just under 30 million won, 104th on the money list. She did not earn a card for 2021. She played in just one more event, the 2021 Korea Women's Open, then officially retired.

Shi Hyun didn't stay "retired" long, however. In May of 2022, she and several other retired female golfers founded the WLPGA, a new golf league to allow senior golfers a place to play organized events. She eventually became the CEO of the league, signing a deal with SmartScore to spread "golf culture" through Korea. Among the former pro players now playing events on the WLPGA are Yoon Kyung Heo, Jeongeun Lee5 (who still is active on the LPGA as well), Hye Youn Kim, Char Young Kim, Soo Jin Yang and Hee Kyung Bae.