The five-year $90m (£52.6m) deal was agreed last week, but league rules prevented the team from formally announcing the contract before July 10.
Owner Dan Gilbert said in a statement: "We are excited that Kyrie has officially committed to be here long term with the Cleveland Cavaliers.
"The future has never been brighter as we are building the team and franchise for sustainable success. Kyrie is obviously a very big piece of our plan."
Irving, who was the number one overall pick in the 2011 Draft, has averaged 20.7 points per game since entering the league.