Isak, who is a product of the AIK academy, made his senior debut for the club at the age of 16 and scored in his debut match against Tenhults IF.
He left the Swedish giants to join Borussia Dortmund, from where he then headed for La Liga with Real Sociedad.
Isak showed enough in Spain to cause Newcastle to want to sign him and the Magpies have paid almost £60m to add him to the ranks at St James’ Park.
He did not feature in Newcastle’s 1-1 draw at Wolves on Sunday due to not having yet received his work permit.
The transfer has gone through though and AIK will now be banking a cash windfall from Newcastle’s big money swoop.
AIK will profit from Isak’s move to Newcastle due to a solidarity payment due and the Swedish outfit will receive 1.75 per cent of the transfer fee, which could come in at just over £1m.
The cash will be a boost for AIK, who currently find themselves sitting fourth in the Swedish top flight following 20 games.