The Canadian, who was sixth overall in 2010, is looking to become just the eighth rider in history to do the Giro-Tour double in the same year.
Britain's David Millar, who has won three stages at the Tour de France, will ride his 11th Tour in support of Hesjedal with Americans Tom Danielson, eighth last year, and Christian Vande Velde, a two-time top-10 finisher, offering a strong line-up in the hills.
Previous Tour stage winner Tyler Farrar will be led out in the sprints by South African national champion Robbie Hunter.
Time trial expert David Zabriskie, Ireland's Dan Martin - who will make his Tour de France debut - and 2010 Paris-Roubaix winner Johan Vansummeren complete the nine-man team.
“We have put together a well-balanced team with an emphasis on support for our leader, Ryder. We have Christian and Tom, both excellent climbers who each have had great GC rides in the Tour and have shown their strength in recent racing," said Garmin directeur sportif Allan Peiper.
"The climbers will have the support of TT specialists David Millar and David Zabriskie along with Johan Vansummeren, who will also be able to help out sprinters Farrar and Hunter in the quest for stage wins.”