The county commission voted 9-4 Monday in favor of the new stadium after nine hours of debate, The Miami Herald reported Tuesday.
"I'm very happy, very pleased,'" said team owner Jeffrey Loria, who won similar approval from Miami City Hall four days earlier.
The new stadium, which is to have 37,000 seats under a retractable roof, is scheduled to be finished by Opening Day 2012.
Of the stadium's $634 million cost, Miami-Dade commissioners pledged $297 million from tourist taxes, $50 million from a bond referendum and $12 million for road and utility repairs, the Herald said. The city of Miami last week pledged $94 million for parking, $13 million toward stadium construction and $12 million for other improvements.
The Marlins have pledged to spend $120 million in the later years of construction and return $35 million of the money borrowed from the county, the Herald reported.