On 20 January 1327 Courtenay was made a knight banneret. In 1333 both he and his father were at the Battle of Halidon Hill. He was summoned to Parliament on 23 April 1337 by writ directed to "Hugoni de Courteney juniori", by which he is held to have become Baron Courtenay during the lifetime of his father. In 1339 he and his father were with the forces which repulsed a French invasion of Cornwall, driving the French back to their ships. The 9th Earl died 23 December 1340 at the age of 64. Courtenay succeeded to the earldom, and was granted livery of his lands on 11 January 1341.