She was a younger daughter of Peter II of Alençon and his wife Marie Chamaillart, Viscountess of Beaumont-au-Maine.

Her brother John I, Duke of Alençon was killed at the Battle of Agincourt against Henry V of England.

Catherine married Peter of Évreux, Count of Mortain, brother of Charles III of Navarre.

One year after Peter's death, Catherine was betrothed again to Louis VII, Duke of Bavaria, brother of Isabeau, Queen of France.

Catherine's husband gave the County of Mortain, from Catherine's dowry to John the Fearless, Duke of Burgundy, to free his wife, during the Armagnac-Burgundian Civil War in 1417, she had been taken prisoner by Bernard VII of Armagnac and did not care for their financial supply.