To attract colonists, he granted asylum to common law criminals, but these caused as much disorder as the pirates they were meant to be a shield against.
Louis XIV of France fought against piracy in the region, but the lack of a substantial garrison caused the British to plunder Port-Cros in 1700 and to invade in 1742 before being driven out by the Jean-Frédéric Phélypeaux, Count of Maurepas.
The marquisate was purchased by the French state in 1815, and changed hands a number of times before being sold to a Dr. Crotte, who tried to develop the island into a tourist resort.
Some facilities for tourists, including a hotel, were built when the island was acquired by Marcel Henry and Claude Balyne.
Vivienne de Watteville lived there from 1929, and wrote a book about her first year on the island, Seeds that the Wind may bring.
During World War II, during the Allied invasion of Provence, the Battle of Port Cros took place on the island on 15 August 1944, in which the German garrison of 150 men fought against a force of American and Canadian commandos, known as the Devil's Brigade.