The 29-year-old forward moves to West London, where he links up with former boss Martin Jol, after playing understudy to Christian Benteke at Villa Park for most of 2012-13.
The 29-year-old has netted more than 100 Premier League goals since 2005, playing for the likes of Charlton, Tottenham and Sunderland, but he started just eight games for the Villans last term due to injury and Christian Benteke's blistering form.
The temporary move will see the forward work with Martin Jol - under whom he played at Spurs - and the Dutchman has insisted that his new man will help boost the club's goal tally this coming season.
“Darren Bent is a striker I have always admired," Jol told the club's official website. "He has shown in the 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 teammates.
"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.”
The Cottagers begin their new season with an away trip to Paolo Di Canio's Sunderland on Saturday.