"It's with mixed emotions that I'm now choosing to step away from the LPGA," Gustafson said on her twitter account. "Thanks for all your kindness over the years."
There was no immediate indication as to whether Gustafson, 39, was giving up all competitive golf.
Gustafson rarely conducts interviews because of a severe stuttering problem. She won 14 times on the Ladies European Tour, where she has been player of the year three times. She has led that circuit in earnings on four occasions.
Gustafson also played for the European Solheim Cup team eight times and has a 13-12-6 record.
She missed the cut Friday in the second round of the Safeway Classic, shooting a 76 that left her in tie for 136th place.