The Hessian administrative court in the city of Kassel said construction on a fourth runway, a third terminal and a cargo and maintenance centre could begin but upheld strict limits on night flights.
The court said it had received more than 200 complaints against the plans, of which it selected 13 as test cases. Most were based primarily on objections to noise pollution and the planned felling of trees in a nearby forest. But it said that the projected economic benefit for the region around Germany's business and finance capital trumped such issues.
"The court ruled that no fundamental concerns stood in the way of the plan to expand Frankfurt Main Airport," it said. "With the expansion, Frankfurt's role as a hub for international air traffic will be secured and strengthened."
Several parties said, however, that they were planning to appeal to a federal court.
Traffic at Frankfurt airport is expected to leap to 88.6 million passengers by 2020 from 53.5 million last year, according to investor forecasts judged as realistic by the court. It also signalled approval of existing restrictions on flights between
11:00 pm and 5:00 am.