The 30-year-old returns to St. James' Park eight-and-a-half years after he left his boyhood club, and has signed an initial one-year deal.
Carroll – who scored 33 goals during his first spell with the club – becomes head coach Steve Bruce's fifth addition of the summer, following the arrivals of Joelinton, Allan Saint-Maximin, Jetro Willems and Emil Krafth.
“It feels very good. My friends and family are here, and it's the club that I support – it is home," said Carroll.
“I enjoyed the time I spent here, and hopefully I can carry on where I left off. When I left eight-and-a-half years ago, I was scoring goals and I was enjoying my football. It's been a pretty tough time since then, and I just want to get back to that.
“I know it's home. I've played here, I've spoken to the fans – I am a fan – and my family is here. For me to get back to where I was, I think this is the only place for me."
Bruce said: “To bring a local hero like Andy back to Newcastle United is fantastic. He is very excited to be home.
“He is a big, physical threat in the opposition box and another great option for us at the top end of the pitch.
“He gives us something different to what we already have and we'll do our best to get him flying again."