McLaren has returned to Rovers after having his contract at Valley Parade cancelled by mutual consent.
The 32-year-old joined the Bantams on a free transfer from Rovers last summer and scored three goals in 35 appearances.
He was one of the club's highest earners but his future was thrown into doubt with Bradford forced to slash their wage bill for this season.
Rovers manager John Barnes said: "I'm thrilled Paul has agreed to come back to the club. He is a very experienced, quality player and I'm glad he is a part of the club's future."
McLaren added: "It's great to be back - in hindsight it was a mistake to leave. I'm looking forward to working with John Barnes and Jason McAteer and can't wait to get playing again."