Nicole was the daughter of Charles, Seigneur d'Avaugour, and Isabeau de Vivonne. Her father was the third son of John I, Count of Penthièvre, son of Charles of Blois and Joan, Duchess of Brittany, but he died in 1434. When her elder uncles, Olivier and John II died, she succeeded to the county of Penthièvre as primogeniture heir. With her succession, she also inherited the Penthièvre claim to the Breton ducal throne. On 3 January 1480, she sold her rights to Brittany to Louis XI of France for 50,000 "livres".