The actress said that Twilight fans will not be disappointed by Pattinson's turn in the forthcoming period drama.
"You get to see a lot of Rob in the movie," she told The Mirror. "Twi-hards? Is that what they're called? Yeah, they will be happy; he's naked most of the time."
The 32-year-old added that she had no reservations about stripping off for her own nude scenes.
"I was pretty relaxed about the nudity. I'm pretty happy with who I am now; that comes with age, as you know your body," she explained.
"Like most women, I have bad days, but I try to eat healthily and work out, and that's what it's about."
Ricci previously admitted that Pattinson is a good kisser.
Bel Ami, which also stars Kristin Scott Thomas and Uma Thurman, is released in the US on March 2 and hits the UK one week later.
> Robert Pattinson's Bel Ami releases new poster
> Bel Ami: New pictures from Robert Pattinson's period drama
Watch the trailer for Bel Ami below: