The crew of Karl Schulze, Phillipp Wende, Lauritz Schoof and Tim Grohmann led from start to finish to win in a time of 5 minutes, 42.48 seconds. Croatia was a length behind in second place after failing to mount an expected late charge, and Australia took the bronze.
The Australians won the 2011 world championship but they and Germany had been upstaged this year by the Croats, who won all three World Cup regattas of 2012 and qualified fastest for the Olympic final.
It was Germany's second gold of the regatta, having also won the blue-ribbon men's eight.
Germany, starting in lane 6 after a late lane reallocation because of strong morning crosswinds, was nearly a second clear of Croatia at the halfway mark. By the 1,500-meter point, the Germans were 1.9 seconds clear and had the race all but won.
Schoof and Schulze stood up, pumped their fists and whooped with delight after their boat crossed the line, 2.3 seconds clear of the Croats.
The Croatia boat of David Sain, Damir Martin and brothers Martin and Valent Sinkovic was looking to clinch the country's first rowing gold since it was declared independent in 1991.