On 31 August 2016, Mulgrew signed for Blackburn Rovers on a three-year contract. He scored his first goal for Blackburn in a 1–0 away win against Newcastle United on 26 November 2016 and later scored a free-kick against them in another 1–0 victory in the reverse fixture on 2 January 2017. He made 30 appearances and scored three times in his first season in the club, but they were relegated to League One. Following this, the "Lancashire Telegraph" reported that Middlesbrough and Hull City were interested in signing him.