 She was the maternal grandmother of King Henry V.

In 1400, she gave the order for the beheading of the Earl of Huntingdon in revenge for the part he had played in the execution of her brother, the 11th Earl of Arundel.The estates which comprised Joan's large dowry made her one of the principal landowners in Essex, where she exercised lordship, acting as arbitrator and feoffee in property transactions.Lady Joan FitzAlan was born in 1347 at Arundel Castle, Sussex, one of seven children, and the eldest daughter of Richard FitzAlan, 10th Earl of Arundel and his second wife Eleanor of Lancaster.