Postecoglou resigned from his position at the helm of the Socceroos after guiding them through playoffs against Syria and Honduras to qualify for the finals of next year's World Cup in Russia.
The 52-year-old replaces Erik Mombaerts, who will leave the club when his contract expires at the end of the month.
"I am excited to be moving to Japan and returning to club football," Postecoglou said in a statement issued by the club.
"Coaching Yokohama F Marinos will be a great challenge and I am very much looking forward to working with the club's players, and young players in particular, to achieve success."
Postecoglou previously led Brisbane Roar to two A-League titles before being appointed the Socceroos coach in the build-up to the 2014 World Cup after Germany's Holger Osieck was fired.
Australia exited the competition in Brazil at the end of the group stage, but Postecoglou was credited with rejuvenating an aging squad and then steered the country to their first Asian Cup title in 2015 when they beat South Korea in the final.
"Ange Postecoglou is an excellent coach, with an attractive and entertaining style of football which will suit our approach," said Marinos President Koichiro Furukawa.
"At the Marinos, we are committed to developing players and Ange has a very strong record in doing this. We are confident that he is the perfect choice to take us forward."
(Reporting by Michael Church in Hong Kong, Editing by Peter Rutherford)
