The 29-year-old defender has signed a two-year deal with the Championship club after his contract expired with Paolo Di Canio's side earlier this summer
The 29-year-old joins the Championship club after his contract at the Stadium of Light expired.
Kilgallon has signed a two-year contract with Gary Bowyer's side, and has been backed by his new manager to make an immediate impact.
"Matt is a good signing for us," Bowyer told the club's official website.
"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 moves to Ewood Park after failing to establish himself as a regular in the Sunderland first team.
The former Leeds and Sheffield United man spent three years at Sunderland, but was sent out on loan to Middlesbrough and Doncaster Rovers during his time at the Stadium of Light.