The Ghanaian winger has linked up with Rafa Benitez's Magpies on a season-long loan with the option of a permanent deal.
"I'm very happy to be at Newcastle," Atsu told the club's official website.
"It's a very big club. They have good facilities and I think Newcastle have one of the best coaches in the world.
"St. James' Park is a fantastic stadium with 50,000 fans; the fans here really love football so much and I can't wait to play at this stadium in front of the fans."
CONFIRMED: Newcastle United have completed the signing of @ChristianAtsu20 on a season-long loan from Chelsea! #NUFCpic.twitter.com/jKZ5Fam9SH
— Newcastle United FC (@NUFC) August 31, 2016