The 29-year-old, who was linked to a number of Championship clubs, has penned a two-year contract at Ewood Park.
Blackburn boss Gary Bowyer: "Matt is a good signing for us.
"He will bring a lot of experience from playing in the Premier League and in the Championship.
"He's left-sided and has the ability to play in a couple of positions for us, both at centre half and at left-back.
"We're delighted that he's agreed to join us and we look forward to working with him."
Kilgallon spent three years at the Stadium of Light.
SUNDERLAND FIXTURES:
Saturday August 17 15:00Premier League Sunderland v Fulham Saturday August 24 15:00Premier League Southampton v Sunderland Saturday August 31 15:00Premier League Crystal Palace v Sunderland Saturday September 14 15:00Premier League Sunderland v Arsenal Saturday September 21 15:00Premier League West Brom v Sunderland Saturday September 28 15:00Premier League Sunderland v Liverpool Saturday October 5 15:00Premier League Sunderland v Man Utd Saturday October 19 15:00Premier League Swansea City v Sunderland Saturday October 26 15:00Premier League Sunderland v Newcastle United
Source: Sunderland-Mad
Source: FOOTYMAD
