Mulgrew re-signed for Celtic in July 2010 after coming through the ranks at the club as a youngster, and grasped his second-chance as a Bhoy with both hands. He never made a first-team appearance before leaving the Hoops in 2006 and joined Wolves before moving on to Aberdeen.
After his return, Mulgrew was a pivotal member of the Celtic first team, earning his first call-up to the full national side in 2012. He continued to be a vital player for his country after Gordon Strachan took charge. Meanwhile, his club form was recognised in 2012 when he was awarded Scotland’s Player of the Year. Mulgrew’s versatility saw him comfortably perform in defence and midfield during his time at Celtic, while also donning the captain’s armband in Scott Brown’s absence.
Mulgrew’s contract with Celtic expired at the end of the 2015–16 season. On 31 August 2016, he signed for Blackburn Rovers on a three-year deal.