Black Cats boss Niall Quinn said: "Kevin came and asked for a move, he wanted to get away. He's been a good servant over the years, but injuries have played a part.
"I feel the move will help Kevin Kyle but also help Chris Brown to come on here, as our targetman. He's up the pecking order now."
Kyle made 109 League and cup appearances for Sunderland after joining from Ayr United in 1999 as a teenager. He scored 19 goals in total.
The Scotland international had loan spells at Huddersfield, Darlington and Rochdale during his time at the Stadium of Light.