"It's with mixed emotions that I'm now choosing to step away from the LPGA," tweeted Gustafson, who has battled a severe stuttering problem. "Thanks for all your kindness over the years."
The 39-year-old Gustafson won the last of her five LPGA Tour titles in 2009. She also won 13 times on the Ladies European Tour and topped that circuit's money list three times.
The long-hitter played in eight Solheim Cups, going 13-12-6. She was 4-0 in Europe's 2011 victory in Ireland and made an inspirational statement at the event by doing a lengthy television interview.
In her final tournament, Gustafson had rounds of 73 and 76 at Columbia Edgewater.