German astronaut Alexander Gerst joined his US colleagues Reid Wiseman and Steve Swanson in cheering on their favourite teams in a video posted on NASA's Instagram page.
"We want to wish all the teams and fans on the ground in Brazil have a great World Cup, have fun and have peaceful games. May the best win," Alexander Gerst said.
The German team will face the US on June 26.
Astronaut Reid Weisman added words of encouragement for the US team.
"Have fun, play hard and we'll be watching on the International Space Station," he said.
The trio have are stationed on the world's largest space laboratory, the International Space Station.
The expedition has a crew of 40 with some members from Germany, Russia and the US - all represented at the World Cup.
More than a dozen countries participate in the $A112 billion space station, which has been operation for 15 years.
NASA says the lab is the length of a football field (109 metres), which made it the perfect place for the astronauts to kick off a game of zero gravity football 370 kilometres above the Earth.
The three will also be watching the game from space, although it's not the first time a sporting event has been seen above Earth.
The Super Bowl XLVIII was recently seen aboard the ISS with NASA astronauts backing the Denver Broncos.
