The 26-year-old former West Ham frontman's move to St James' Park was rubber-stamped this afternoon, the Premier League club have confirmed.
The arrival of Ba, who scored seven times in 13 appearances for the Hammers during the second half of last season, comes 24 hours after Magpies skipper Kevin Nolan headed for Upton Park in a deal believed to be worth in the region of £4million.
Pardew said: "Demba made a great impression with West Ham last season and is a great signing for this club.
"He has pace, excellent technical ability, is good in the air and, it goes without saying, has the ability to consistently find the back of the net.
"Moreover he has a great passion to play for Newcastle United."
Newcastle beat off competition from a series off other suitors to land the former Hoffenheim player as Pardew looks to increase his options in attack.
The player seemed to be heading for Stoke in January until he failed a medical on a knee problem and was snapped up by the Hammers.
Despite his best efforts to keep the Londoners in the Premier League, they were relegated at the end of last season, but not before he had proved both his fitness and his prowess in front of goal.
Ba, who was born in the Paris suburb of Sevres and is one of eight children, began his career with Rouen.