Capt Schmidt and Mr Bierdel were put on trial in 2006
An Italian court has acquitted three members of a German charity of aiding illegal migration after they rescued a boatload of stranded African migrants.
In 2004, a ship from the Cap Anamur relief group rescued 37 migrants who were stranded in the Mediterranean Sea.
Former Cap Anamur president, Elias Bierdel, as well as the ship's captain and first officer, were put on trial in Agrigento, Sicily in 2006.
Humanitarian groups have welcomed the ruling.
The UN refugee agency had complained that the trial, as well as Italy's tough legislation on illegal immigration, had scared fishermen from rescuing people stranded at sea.
Italy had at first turned away the ship, but let it dock after nearly three weeks when the captain issued an emergency signal.
The three aid workers were detained for several days and then faced trial.
"This verdict is important for all those who do good," said the ship's captain, Stefan Schmidt.
"My only regret is that with the money we have spent fighting this case for five years we could have been helping people," he was quoted as saying by Reuters news agency.
All 37 migrants were returned to their home nations after landing in Sicily. Many had claimed they were fleeing fighting in Sudan's troubled Darfur region, but were found to come from Ghana and Nigeria.
Italy, with its long and porous coastline, is a major target for migrants seeking to enter Europe.