After passing his medical at the club's Apperley Bridge training ground, Kilgallon has penned a one-year deal with the Bantams to become City's eighth signing of the summer.
The defender's deal with the club also includes the option of a further year.
Kilgallon, who took part in training with his new team-mates for the first time this Monday, joins City after leaving previous club Blackburn Rovers at the end of last season.
The centre half, who can also play as a full back, has previously featured in the Premiership for Leeds United, Sheffield United and Sunderland.
The rest of Kilgallon's professional career has been at Championship level ahead of his move to the Northern Commercials Stadium.
While at Sheffield United, Kilgallon first linked up with City boss Stuart McCall, who was the Blades' assistant manager at the time.
Speaking about Kilgallon's arrival, McCall said: "We're delighted to have brought in someone of Matt's pedigree and experience.
"I've spoken to a number of people at Blackburn Rovers and they were all very positive about him.
"He's coming here hungry and desperate to still play at the highest level possible.
"He feels that coming to Bradford will give him the opportunity to play higher up again.
"Killa (Matthew Kilgallon) has played the majority of his career at centre back but I saw him a couple of times playing at left back last season for Blackburn in the Championship, and playing well.
"I obviously know Matt from his days at Sheffield United and Greg (Abbott, Head of Recruitment) knows him from his time at Leeds United.
"We knew we needed to still add to our defensive options for the new season.
"We lost (Christopher) Routis, Greg (Leigh) and Reece Burke from last year and we'd only really brought Nat (Knight-Percival) in. With (Stephen) Darby and (Rory) McArdle still injured as well, it was certainly an area we needed to strengthen.
"Matt ticks a lot of boxes and we now have that genuine competition for places both at centre back and at left back."
Born in York, Kilgallon made his senior debut with Leeds having come through the youth ranks at Elland Road.
On top of his games in the Premier League with Leeds, Kilgallon also appeared in Europe and in the Championship for the Whites, helping them to the Play-Off Final back in 2006.
During his time with Leeds, Kilgallon also enjoyed a brief loan spell with West Ham United in 2003.
After five years as a professional at Elland Road, Kilgallon made the move to fellow Yorkshire side Sheffield United.
The 6' 2'' defender signed on at Bramall Lane for a fee of £1.75 million, rising up to £2 million with add-ons.
Kilgallon spent three years with the Blades, winning their Player of the Year for the 2008-09 season, before securing a move to Sunderland in January 2010.
While at the Stadium of Light, Kilgallon also played for Middlesbrough and Doncaster Rovers on loan.
Following three years with the Black Cats, Kilgallon signed with previous club Blackburn in 2015.
Along with his domestic appearances, Kilgallon has also picked up five caps at Under-21 level for England.