She was the second eldest daughter of the French prince Charles, Count of Valois, and Margaret, Countess of Anjou and Maine.

[1][3] In 1299, Joan's mother died, probably in childbirth, and her father married his second wife, Catherine I of Courtenay, Titular Empress of Constantinople, by whom he had four more children.

[3] During the many absences of her spouse, Joan was left to handle the economy and political affairs of the realms, receive diplomats and travel between Hainaut and Holland to maintain control.

[citation needed] After her husband William I died in 1337, Joan took the veil and entered into Fontenelle Abbey in Maing.

The fact that she took the veil did not mean that she retired from the world: she maintained her own chancellery and personal staff, received guests from court and was kept up to day in political affairs.