Froome is the favourite for the 2014 edition of cycling's most famous race - an event that will begin in England before crossing into France.
Australian Porte has played a crucial role at Team Sky in recent years and his work as a lead-out man for both Bradley Wiggins and Froome has helped them clinch the last two Tour wins.
Porte was set to ride the Giro this year in an attempt for overall victory but has been sidelined by gastroenteritis.
He missed the Tirreno-Adriatico as a result and then withdrew from the Volta a Catalunya - and in a bid to get fit for the Tour, he has now shelved his plans for Giro domination.
Team Sky's head of performance support, Tim Kerrison, said the decision was designed to give the team the best possible chance in the Tour.
"Richie was always going to ride the Tour de France this year but this now means that he can fully focus on being in the best possible shape without having the added challenge of having to ride the Giro as well," he told Team Sky's website.
"He played an invaluable role in our Tour wins in 2012 and 2013 and we want him to do the same again this year.
"We're always reviewing our line-ups and looking how we can best support our riders and give ourselves the best possible chance for success."
Porte will now join Froome for the Liege-Bastogne-Liege later this month.
Team Sky also revealed that Wiggins would feature at Sunday's Paris-Roubaix.
Other cycling news on Monday saw Mark Cavendish withdraw from the Grand Prix de l'Escaut because of flu.
Cavendish has missed several races with the illness but is still likely to feature at the Giro, with a potential return coming at the Tour of Turkey, which starts later in April.