Colback was out of contract at the Stadium of Light at the end of last season and Newcastle have now moved to bring him in on a long-term contract.
The midfielder is thankful to Sunderland for everything they did for him, having been at the club since his youth career, but admits he will be fulfilling a boyhood dream to play for the Magpies.
“I'm absolutely delighted,” he told Newcastle’s official website.
"To come to the team I supported as a boy, my hometown team, will be really special for me.
"It was an opportunity I couldn't let slip. If you asked fans around the world the one thing they'd like to do before they die, it would be to play for the team they support and I've got the chance to do that.
"I've only got good things to say about Sunderland. They gave me my chance and I want to thank the fans and the club for all their support.
"I hope they can understand the chance I've had here to move to my boyhood club. Now I can't wait to pull on the black and white shirt at St. James' Park for the first time."
Newcastle manager Alan Pardew is also excited about the deal and has backed Colback to be successful at St James’ Park.
"I'm extremely pleased to have brought Jack to Newcastle United,” said Pardew.
"He's a great passer, versatile and rarely gives the ball away. He's also a local lad and knows exactly what playing for this club means.
"And at 24-years-old, his best years are ahead of him so I think he'll be a big asset to us."
Sunderland have also responded to the move, making their disappointment clear and suggesting that Colback had indicated he would stay.
A statement read: “Jack is a player we have nurtured and developed through our academy system since he was eight years old.
“We gave him the opportunity to become a professional footballer and are therefore extremely disappointed in the events that have led to his departure from the club.
“This wasn’t about money - the club agreed to all of the terms demanded of us during discussions and we were always led to believe that Jack wanted to stay with us.
“At his and his representatives’ request, final talks were put on hold until the club secured its top flight status. To our dismay however, we were subsequently never given the chance to negotiate with him to stay.
“For him to then leave the club that has supported him throughout his formative years in such a manner, with no chance for Sunderland to recover any of the significant investment that it has made in him as a player, has left a bitter taste.”