The 25-year-old will link up with former Gers teammate Joey Barton at the League One outfit, with the former Manchester City player having taken charge at the club this summer.
"I'm delighted that Jason has joined us here at Fleetwood Town," Barton told the club's website.
"I saw his qualities when I was at Rangers on a daily basis, and as soon as I found out he was available we tried everything to make sure we got him here.
"He's a great character, a great trainer and he knows the level after his season with Sheffield United. It's a huge signing for us."
Holt played 33 times for Rangers last season.