The 25-year-old brother of England international Steve was released by Durham at the end of last season.
He has averaged 34.66 with the ball in 37 first-class matches, and 26.10 with the bat.
He told the club website: "I am delighted to have signed for Kent. I cannot wait to get down to Kent and start training with the squad."
The former England Under-19 player continued: "I am looking forward to an exciting 2012 season. This is a great opportunity and I look forward to continuing my career with a county hungry for success."
Kent chairman of cricket Graham Johnson said: "I am delighted that we have signed Ben - he offers a lot with both bat and ball, and he was a target for us during the recent recruitment process.
"He has a point to prove about making the best of his undoubted ability and we look forward to helping him do that. I am sure that all involved with Kent Cricket will make him very welcome."
Kent have signed former Durham all-rounder Ben Harmison.