Arnauld de la Perière remained in the German Navy after the war ended. During World War II, he was recalled to active duty as a vice admiral, but was killed in a plane crash near Paris in 1941 while taking part in secret negotiations with the Vichy French government.
At the outbreak of the First World War, Arnauld de la Perière served as an adjutant to admiral Hugo von Pohl in Berlin. Upon the mobilization, he was transferred to an active post where he served in the Marine-Luftschiff-Abteilung. In 1915, Arnauld de la Perière transferred to the U-boats. After a course in Pola, he was given command of the U-35 in November 1915. He made 14 voyages with the U-35 during which he sank 189 merchant vessels and two gunboats for a total of . Transferred to the U-139 in May 1918, he sank a further five ships with a combined tonnage of . His record number of sunken ships and tonnage are both unsurpassed since then. For his service, he was awarded the Iron Cross, second and first class and the Pour le Mérite in 1916.
At the start of World War II Arnauld de la Perière was again called up for active duty. Until March 1940, he served as naval commandant in Danzig until he was sent to the Low Countries as naval commandant for Belgium and the Netherlands. Promoted to rear admiral, Arnauld de la Perière was made naval commandant in Brittany and later for the entire western French seacoast. He was promoted to vice admiral on February 1, 1941. Transferred to take up command as Admiral South, he was killed when his plane crashed on take off near Le Bourget Airport. He is buried in the Berliner Invalidenfriedhof.