The Portuguese coach, who will be doing punditry work for Russian channel RT during the tournament, believes that his home nation and Argentina will benefit from Cristiano Ronaldo and Lionel Messi in their ranks.
Mourinho also thinks that the Selecao have been transformed by manager Tite, while Spain boast a mix of experience and quality, but nonetheless believes that there could be a surprise package in Russia.
"Players like [Lionel] Messi and [Cristiano] Ronaldo are so good that they can make their teams better than they are on paper," Mourinho told GQ. "So I think Argentina and Portugal can do well.
"Brazil, because of their manager Tite, can play well tactically and defensively, but they still have that natural Brazilian talent. They will be a team to watch.
"And of the European teams, Spain looked really strong in qualifying. They have a mix of good experienced players and quality players. But you never know... there can always be a surprise at the World Cup."
Mourinho's native Portugal will be going into the tournament hoping for back-to-back triumphs in major competitions after winning Euro 2016.