Mitchell, who is 23, started his career at Middlesbrough eight years ago when Darlington manager Alun Armstrong was on the coaching staff, and after loan spells at Harrogate and Inverness, moved to Sunderland in 2020.
He made one appearance for the Black Cats before moving across to the USA, joining Inter Miami in Florida and then Hartford Athletic in Connecticut. After trials at two other clubs, he has returned to the north east and joined Quakers as he continues his career in English football.
Alun said; "I know Mitch from our days at Middlesbrough, and what he's capable of. I'm looking forward to seeing him in action again."