The 18-year-old has built a reputation as a technically gifted player since joining City's Academy aged nine and will initially link up with Newcastle's Professional Development Phase (PDP).
An impressive 2022/23 saw Harrison help City's youngsters to the Under-18s Premier League title and he has continued that form this season with eight goals and four assists to his name.
On joining the Academy, Harrison said: "The size of the club and what it has got going for it is massive for me. It's got a huge, passionate fanbase and I'm looking to really push on with my career now.
"If I was a kid now, looking at me signing for Newcastle United, it's what dreams are made of. I'm really looking forward to what is coming and how I can progress in the coming years.
"I'm an effective player who can add goals and assists. I really like to create stuff but, on the other side, I'd also say I'm a very passionate player who always wants to win."
Academy Director Steve Harper added: "We are delighted to secure Alfie's signature. His hunger to represent Newcastle United and continue his development here was obvious from the outset.
"He's a passionate, talented player who we are really looking forward to welcoming to the club and ultimately seeing in a black and white shirt.
"Alfie's signing is part of a strategic move to make our PDP group younger, particularly the Under-21s, and I would like to thank the board and everybody involved at the club in making this move happen."