He has been at the club for three years and the Mackem chairman Bob Murray has terminated his contract and the ex-Millwall gaffa has left the club with immediate effect.
Murray: "As chairman, I take responsibility for what has proven to be an unsuccessful and heartbreaking season, despite the best intentions, efforts and expectations of every one at the club.
"I feel deeply sorry that the excitement, optimism and aspirations of all Sunderland fans looking forward to a return to the Premier League have been rewarded in this way, and I apologise for this.
"It is especially tough on supporters who have turned out in numbers week in week out, despite seeing so little to raise their spirits.
"It is hard to see such loyalty unrewarded and I am sorry that performances and results have not mirrored the tremendous level of support that the club has been given.
"The club did not return to the Premiership just to make up the numbers and whilst we fully expected it to be a tough first season back, none of us expected to be in the position we are today.
"I would like to thank Mick McCarthy for his efforts for the club whilst at Sunderland and wish him and his family the best for the future.
"Looking ahead, we will be taking our time to appoint a successor for what will be another very important season for the club in 2006."