On 12 August 1915, U-3 was damaged after an unsuccessful torpedo attack on an Italian armed merchant cruiser and, after she surfaced the next day, was sunk by a French destroyer.
Dana 12. kolovoza 1915. godine U-3 je oštećen nakon neuspješnoga torpednog napada na talijansku naoružanu trgovačku krstaricu, a nakon što je sljedećega dana izronio na površinu potopio ga je francuski razarač.