The son and heir of John Fitzalan, Lord of Oswestry and Clun, from Shropshire.
His mother was Isabel, the daughter of William d'Aubigny, 3rd Earl of Arundel by his wife, Mabel of Chester.
John obtained possession of his paternal estates on 26 May 1244, aged 21 years.
John Fitzalan was a surviving member of the English force that was defeated at the hands of the Welsh at Cymerau (near Nantgaredig) in Carmarthenshire.
From 1278 to 1282, his sons were engaged in Welsh border hostilities, attacking the lands of Llywelyn.