The pop star will wear a Rovers top with the number 28 on the back throughout the 2013/14 season and, as part of the deal, he'll play for the club's development squad.
Thrilled Tomlinson, who hails from Doncaster, says, "This has always been a childhood dream for me. I feel very honoured to have been asked to sign for Rovers."
The singer will donate the cash he has received from the club deal to the town's Bluebell Wood Children's Hospice.
He adds, "Being able to help both the club and the amazing charity Bluebell Wood is what it's all about."