Alan Pardew landed the player on a five-and-a-half year deal from German side Freiburg.
The 26-year-old Senegal international will join compatriot Demba Ba in the Magpies strikeforce once the pair return from duty at the African Nations Cup and Pardew admitted he was delighted to get his man.
Alan Pardew: "Ever since Andy Carroll left, Papiss was my first choice in the specific role he has had at the end of the play.
"He is a finisher with an already-established CV in the Bundesliga, where we have monitored him for the best part of two years.
"Unfortunately he was out of reach, financially, for us in the summer, but it recently became apparent that Derek Llambias (managing director) and Lee Charnley (club secretary) could do the deal in this window.
"I spoke to Demba about Papiss, and he cannot wait to join up with his team-mate in Newcastle.
"Our fans know that this shirt brings its own pressures. One of the iconic numbers in world football - the number nine of Newcastle.
"It will be only fair that Papiss is given time to understand the responsibility it brings. As the manager, I wish him all the luck in the world to bring success to himself and this club."