Palace boss Dougie Freedman told the club website: "I'm delighted to add another player of international calibre to the club.
"Jonathan's a quality left-sided player with huge potential and an exciting addition to our squad."
Parr added: "I know it's a tough league, a physical league and I know it was a tough season last year for the club.
"But I hope it will be a better season this year and I'm really looking forward to coming here."
Source: BBC Sport
Source: BBC Sport