Ahn turned professional in 2002 and that year she topped the order of merit on the Apache Dream Tour (the KLPGA's developmental tour) after winning three times. In 2003, she won the CJ Nine Bridges Classic, an LPGA Tour sanctioned event in her home country. At 19 years, 1 month and 18 days she was the youngest non-American winner in the tour's history.
Ahn began her professional career in 2002 and quickly rose to the top of the Apache Dream Tour rankings after winning three times that year. In 2003, she secured the CJ Nine Bridges Classic title on the LPGA Tour, a victory in her home country. At 19 years old, she established herself as the youngest non-American winner in tour history.