On February 20 he took up his commission as Lieutenant Governor of the Isles of America and Captain general of the French at St Kitts. He arrived wearing the regalia of the Knights of St John and soon dispensed with the authority of the French king, declaring "The people of St Kitts will have no other Governor than De Poincy and will take no orders from the King of France."
By 1642 he started building the Chateau de Montagne on his estate called La Fontaine. This was an elaborate building with a collection of exotic plants in the grounds. Ponciana Regia is named after him.
He had a Town Hall erected in Basseterre in what is now known as Church Street. This served as his administrative centre, where he dispensed justice and administered the colony.
When the French king sent De Thoissy to relieve him, de Poincy refused to let him land. Eventually de Thoissy was sent back to France in chains. The Capuchins were also expelled at this time for taking the side of de Thoissy. The Jesuits were invited in to take their place.
When de Poincy died at the age of 77, he was buried in Basseterre, probably in the grounds of what is now St George's church. he was credited with turning Bassterre into a successful trading port. Some of the dancers in the annual carnival are said to be descended from a troupe of Acrobats who were his slaves.
Philippe de Lonvilliers dePoincy, a strongman official of the Knights of Malta, dispatched 160 of his best troops and succeeded in deceiving the Spanish garrison to capitulate and sail for San Juan.
DePoincy spared no expense nor effort to develop the fertile land of St. Croix.
dePoincy died in 1660 and was succeeded by Chevalier de Sales as Governor of St. Christopher.