Leicester boss Claudio Ranieri, who replaced Nigel Pearson in the summer, watched Jamie Vardy head an early opener before a brace from Algerian Riyad Mahrez put the buoyant Foxes out of sight before half-time.
Mahrez, who signed a new deal at the club last week, missed two fine chances to complete his hat-trick before Jermain Defoe gave Sunderland a glimmer of hope by firing past Kasper Schmeichel.
Marc Albrighton put the seal on Leicester's win in the 66th minute and despite Steven Fletcher's late consolation it marked a worrying start to the season for Dick Advocaat's men.
Sunderland manager Dick Advocaat said in a press conference today that his transfer window acquisition spree is not yet over.
He plans to add another two players to his squad, on top of the five he has already signed this summer.
When asked what's the key to avoiding relegation this season, he said: "bringing in good players".
Advocaat would not be drawn on which players he is considering.
Watch the full press conference here.
Sunderland boss Dick Advocaat says his summer spending is far from finished as he aims to make his current crop of Black Cats stars fight for their first-team future.
Advocaat has completed five new deals since making his own role at the Stadium of Light permanent at the end of last season, and is eyeing at least two before before the end of the transfer window.
The Dutchman believes many of his side's problems during the last campaign came about because a number of players were able to rest on their laurels with their places in the starting line-up assured.
"The most important thing is that you have competition - that everybody has to fight for their places. You can see now in training that that is improving."
Jeremain Lens is expected to join Jermain Defoe up front in his new side's season-opener at Leicester on Saturday, but there will be no place for fellow new boy Yann M'Vila.
The French international is short of match fitness after arriving on a season-long loan from Rubin Kazan this week, and is instead expected to start with the reserve squad.
Jeremain Lens has given his first press conference since joining Sunderland from Dynamo Kiev in June.
He said that although he and manager Dick Advocaat are not 'best friends' they know what to expect from each other.
Lens also said he planned to make it five wins in a row for Sunderland against local rivals Newcastle United.
He was also asked about his favourite playing position - he plans to stay on the right for now.
Jeremain Lens has given his first press conference since joining Sunderland from Dynamo Kiev in July.
He said he was excited about the upcoming season, and that "playing in the Premier League is a dream come true."
"I had freedom working with Dick Advocaat last time, I hope it will be the same now" @itvtynetees Jeremain Lens talking to the press
Sunderland striker, Connor Wickham, is set for a shock move to Crystal Palace.
A London source told ITV News Tyne Tees the two clubs have agreed a fee for the 22-year-old. Wickham only signed a new long term contract at the Stadium of Light last season, but he's set to head south for talks with Palace on Friday (31st July).
Sunderland AFC defender Santiago Vergini has joined Spanish La Liga side Getafe CF on a season-long loan deal with a view to a permanent transfer.
The 26-year-old Argentine arrived on an initial loan deal in 2014, going on to make 51 appearances in 18 months on Wearside.
Dick Advocaat has spoken about the kind of squad he wants for Sunderland ahead of the season starting.
Catch our reporter Frances Read's full interview in tonight's programme at 6pm.
The editor of A Love Supreme, Martyn McFadden, hopes, after three managers in just over two years, the club can now build and progress:
Martyn McFadden, editor of Sunderland fanzine A Love Supreme, says former manager Dick Advocaat will always be fondly remembered by fans. The Dutchman stepped down after helping the club avoid relegation: