Kári Árnason was called up to the senior Iceland squad in March 2005 for the game against Croatia and he made his debut four days later against Italy.
He scored his first goal for his country seven months later in October 2005 against Sweden at Råsunda.

He was selected by Lars Lagerbäck for UEFA Euro 2016 where Iceland made their first ever appearance in a major tournament.
In the first game he marked Cristiano Ronaldo out of the game in their draw with Portugal, the team that eventually won the entire tournament.
In their last group stage game Iceland were able to beat Austria to advance to the knock-out stages, and he notched an assist and was selected as man of the match.
He once again assisted a goal in Iceland's upset victory over England in the round of 16.

In May 2018 he was named in Iceland’s 23 man squad for the 2018 World Cup in Russia.
Kári Árnason was called up to the senior Iceland squad in March 2005 for the game against Croatia and he made his debut four days later against Italy. He scored his first goal for his country seven months later in October 2005 against Sweden at Råsunda.
He was selected by Lars Lagerbäck for UEFA Euro 2016 where Iceland made their first ever appearance in a major tournament. In the first game he marked Cristiano Ronaldo out of the game in their draw with Portugal, the team that eventually won the entire tournament. In their last group stage game Iceland were able to beat Austria to advance to the knock-out stages, and he notched an assist and was selected as man of the match. He once again assisted a goal in Iceland's upset victory over England in the round of 16.
In May 2018 he was named in Iceland’s 23 man squad for the 2018 World Cup in Russia.
Kári Árnason