The 3rd Baron de Mowbray was reportedly in Edward III's good graces, being present in France in the War of the Breton Succession for the sieges of Nantes and Aguillon.

He was also on the English side at the Battle of Neville's Cross in the Second War of Scottish Independence.

He died of the plague at York on 4 October 1361, and was buried at the Friars Minor in Bedford.

[2] He married firstly, before 26 February 1322, Maud de Holand, daughter of Robert de Holland, 1st Baron Holand, by Maud la Zouche, daughter and coheiress of Alan la Zouche, 1st Baron la Zouche of Ashby.

[3] He married secondly, between 28 February 1327 and 4 June 1328, Joan of Lancaster, sixth and youngest daughter of Henry, 3rd Earl of Lancaster, by whom he had a son and two daughters:[3] He married thirdly, by papal dispensation of 4 May 1351, Elizabeth de Vere (d. 14 or 16 August 1375), widow of Sir Hugh Courtenay (d. before 2 September 1349), and daughter of John de Vere, 7th Earl of Oxford, by Maud de Badlesmere, daughter of Bartholomew de Badlesmere, 1st Baron Badlesmere.