The 29-year-old, capped 13 times by England, joined Villa from Sunderland in Jan. 2011 but spent much of last season on the bench after falling out of favour. He had been a prolific scorer on Wearside, netting 36 goals in 63 appearances.
"Darren Bent is a striker I have always admired," Fulham manager Martin Jol said on the club website (www.fulhamfc.com).
"He has shown in the Barclays Premier League that he is composed and clinical in front of goal but, even if he is not scoring, he is involved in some good link-up play, creating opportunities for his team mates.
"I'm delighted that he has joined us, he gives us pace up front and I am confident that he will add to our goals scored tally this season."
Fulham, who finished 12th last season, kick off their Premier League campaign away to Bent's old club Sunderland on Saturday.