The Italian sprinter has won 10 grand tour stages since 2007. He had five individual wins this season, including the penultimate stage of the Vuelta a Espana.
“I am sure Bennati will start the year strong and aim for results at our race as the first WorldTour race of the season,” race director Mike Turtur said.
Voigt, 40, last rode the Tour Down Under in 2010. “We look forward to welcoming back Jens Voigt. Not only is Jens is a three time Tour de France stage winner, he is an absolute crowd favourite.”
The team is also sending its two New Zealand riders, national road champion Hayden Roulston and Jesse Sergeant.
“RadioShack-Nissan-Trek has selected an impressive line-up to include a mix of Grand Tour experience and youthful competitiveness in their Santos Tour Down Under squad,” Turtur said.
Jose Azevedo will serve as team manager for the race, which is held in southern Australia from January 15 to 22.
RadioShack-Nissan-Trek for the Tour Down Under: Daniele Bennati (Ita), Linus Gerdemann (Ger), Ben Hermans (Bel), Tiago Machado (Por), Hayden Roulston (NZl), Jesse Sergent (NZl) and Jens Voigt (Ger).
Meanwhile, the newly-merged team is continuing its first pre-season training camp in Calpe. For a new gallery of images from Spain, click here.