The 30-year-old striker has been without a club since leaving Malaysian outfit T-Team earlier this year and he has penned a three-month deal with the Bantams, subject to international clearance.
Folan, who lists Hull City, Wigan Athletic and Leeds United amongst his former employers, has been training with the League One side and boss Phil Parkinson hopes he will offer his side something different up front.
"Caleb is a powerful striker who will add a different option to our front line," Parkinson told Bradford's official website.
"He has been playing his football abroad for the last couple of years and he is now very keen to rebuild his reputation back in this country.
"He has looked great for us in training and we look forward to working with him on a more permanent basis now.
"We've been looking for someone to give us that little bit extra competition up front and Caleb gives us that. He has the strength to be a real handful for defenders to deal with."