Real Sociedad have announced that Isak is to remain at the club for another nine years after signing a new contract.
The Swedish striker has agreed terms on a deal which will keep him at the Estadio Deportivo de La Coruna until June 2029.
The agreement was confirmed by both clubs and follows a successful season for Isak, who scored 15 goals in all competitions as he helped the Basque side finish in third place in La Liga.
"Isak is one of our key players and we're very pleased that he's going to stay with us for many more years," said Real Sociedad sporting director Kike Sancho.
"He's had a fantastic campaign this season and it's clear that he's been a big part of our success."
The news comes just days after Isak's agent, Janne Jensen, revealed that the forward would be looking for a move away from Real Sociedad in the summer.
However, the club were able to secure his services for the long-term future, with Isak set to continue playing for them for the next decade.
The agreement also means that Isak will not be eligible to play for the Sweden national team during this period, although he can still represent his country through the youth system.
Overall, it looks like Isak will be staying put at Real Sociedad for the foreseeable future, with the club now looking to build upon their impressive showing last season and continue their upward trajectory in La Liga.