HMS Ilex was launched on 28 January 1937 and commissioned on 7 July of the same year.

At the outbreak of WWII, Ilex was deployed in the Mediterranean with the Third Destroyer Flotilla. She was immediately transferred with her Flotilla to the Western Approaches for convoy escort duty. On 13 October under the command of Lieutenant Commander Philip Saumarez she attacked and sank U-42 south-west of Ireland in company with the destroyer HMS Imogen

The first half of 1940 saw Ilex conducting Fleet screening duties in and around the North Sea. In May she transferred to the Second Destroyer Flotilla for service in the Mediterranean. On 27 June 1940, in company with HMS's Dainty, Defender and Decoy plus HMAS Voyager she depth-charged and Italian submarine off Crete. The submarine was forced to the surface and scuttled by her crew. Two days later, on 29 June, the same ships attacked and probably sank another Italian submarine.   On 29 June Dainty and Ilex shared in the sinking of a third Italian submarine south-west of Crete. Ilex participated in the Battle of Calabria and on 19 June she escorted HMAS Sydney during the sinking of the Italian cruiser Bartolomeo Colleoni off Cape Spada, rescuing 230 survivors.

She escorted HMS Illustrious during the attack on the Italian Fleet at Taranto.  On 20 March 1941 she formed part of the destroyer screen for the fleet at the Battle of Cape Matapan. On 14 June she suffered major structural damage from dive-bombing and was towed to Haifa and underwent a series of temporary repairs before sailing for the USA for a refit and full repair.

In March 1945 she was reduced to "reserve category C" at Malta". She was placed on the disposal list in August. Ilex was sold for scrap on 22 January 1946 and broken up in Sicily in 1948.