The former Everton striker, once signed by Arsenal for £7million, moves from Blackburn Rovers in an undisclosed deal worth around £700,000.
Jeffers, who will wear the number nine shirt vacated by Steve MacLean, has been desperate for first-team football after falling down the pecking order at
On the completion of the deal, which ends Brian Laws' summer-long search for a striker, he told the club's official site: "I am delighted, obviously. It's a massive football club and I think they are in the wrong division at the moment.
"It's a chance for me to show people what I am all about. A lot of people have written me off but one thing I will do when I get regular games is score goals and I always have done wherever I've been."
Laws added: "Francis has spent most of his career in the Premier League because of the quality that he possesses and I believe he can be a regular scorer with us in the Championship."
Jeffers is set to make his debut in the season opener at