Fleming forced to fly Eagles nest
The veteran defender's existing deal expires at the end of the season and a persistent leg injury has put paid to his chances of claiming a new one.
The 35-year-old has not played for The Eagles since early January, but Dowie admits the decision to release him was not an easy one.
"He's one of the best professionals I've ever worked with, he's been at the heart of everything I've tried to do," said the Selhurst Park chief.
"It's just a shame he got injured when he did.
"He's a great leader and offers so much around the place.
"I wanted to tell him early because he deserves that."
Fleming was brought to Palace in December 2001 from Middlesbrough by then manager Trevor Francis.