The announcement comes days after team manager Patrick Lefevere said the British sprinter will stay home for the Grand Tour, which begins on Saturday.
Sam Bennett was expected to compete in the race and defend his green jersey, but failed to recover from a knee injury, with Cavendish taking his place and looking to add to his tally of 30 stage wins on the Tour de France.
“I am delighted to be returning to the Tour de France with Deceuninck – Quick Step,” Cavendish, 36, said in a team statement.
“Obviously the circumstances with Sam could be better – he had a Special Tour last year and I’m sad he can’t defend his green jersey.
“But at the same time, I am delighted to come back to a race with which I have such an affinity and where I have so much history. “
Cavendish, back with Deceuninck-Quick Step six years after leaving the Belgian squad, will take part in the Tour for the first time in three years.
He is in great shape this year, winning four stages of the Tour of Turkey and then the fifth stage of the Tour of Belgium.