The 22-year-old former Derry City midfielder has been rewarded for his meteoric rise on Wearside just seven months after his ?500,000 switch to the Black Cats on a three-year deal.
McClean said: "I'm thrilled to be here. I'm really enjoying my football and to have earned a new contract is a dream. I'm over the moon to see my next three years with Sunderland."
McClean was signed by former manager Steve Bruce, but made his senior debut as a substitute in his successor Martin O'Neill's first game in charge, a 2-1 Barclays Premier League victory over Blackburn on December 11.
His first start arrived on New Year's Day in a famous 1-0 win over Manchester City, and he has remained in the team ever since.
O'Neill said: "I am absolutely delighted that James has committed himself to the club.
"He has had an explosive start to his career here at Sunderland and long may it continue."
McClean's form for his club sparked a clamour for recognition by the Republic of Ireland at senior international level, and the Derry-born player was belatedly added to Giovanni Trapattoni's squad for last month's 1-1 friendly draw with the Czech Republic.
He was introduced as a late substitute to rapturous applause from the home fans at the Aviva Stadium, and the debate over whether or not he has a chance of going to the Euro 2012 finals has been raging ever since.
In the meantime, McClean has the prospect of Tuesday night's FA Cup quarter-final replay against Everton and the promise of a trip to Wembley to face Liverpool if Sunderland can see off David Moyes' men as a thrilling first season in England approaches its climax.
Source: PA
Source: PA