Although the fee was undisclosed, it is likely to be the biggest of the January transfer window so far with local media reporting it is around 10 million pounds.
The 26-year-old must wait to make his debut as he is on international duty at the Africa Cup of Nations.
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"It is an honour to play for such a big club and I am looking forward to it," Cisse told Newcastle's website.
Newcastle manager Alan Pardew said Cisse had been a target ever since Andy Carroll's transfer to Liverpool in the last January transfer window but had been out of reach financially.
Cisse will wear the number nine shirt, vacated by Carroll and which has been worn by club greats such as Alan Shearer.
"I am aware of the huge importance of the number nine shirt, and when I spoke to the manager he made it very clear how important this shirt is," he said.
"I will treat it with the respect and I hope to do my very best in this shirt."
Cisse scored 37 goals in 65 appearances for Freiburg and Newcastle will be hoping for a similar record for them.
"He is a finisher with an already-established CV in the Bundesliga, where we have monitored him for the best part of two years," Pardew said.
"It has become obvious this season that the team and the club have done exceptionally well, and [owner] Mike Ashley has backed me to bring this player to the club," added the manager, whose side lie sixth in the Premier League.
"In the short-term of course, he is at the Africa Cup of Nations, but the competition he will bring to our squad when he joins up with us should inspire the players and reassure them of this club's ambition."
