The ship had a particularly active operational role during World War II, being awarded 11 battle honours, and was known as "The hardest worked destroyer in the Fleet".

[3] The ship carried a maximum of 490 long tons (500 t) of fuel oil that gave her a range of 6,500 nautical miles (12,000 km; 7,500 mi) at 15 knots (28 km/h; 17 mph).

[6] While under repair in May–June 1940, her aft bank of torpedo tubes were replaced by a QF three-inch (76 mm) 20 cwt[Note 1] AA gun.

[10] Faulknor was completed on 24 May 1935 at a cost of £271,886, excluding items supplied by the Admiralty such as guns, ammunition and communications equipment.

[11] After working up in May–July, the ship to put into Portsmouth to remedy the defects revealed from 29 July to 21 September, before she could assume her proper place with her flotilla.

[12] Faulknor, together with most of the ships of her flotilla, was sent to reinforce the Mediterranean Fleet during the Second Italo-Abyssinian War;[12] during this time, Captain Victor Hilary Danckwerts relieved Clarke in March 1936.

Faulknor collided with the freighter SS Clan MacFadyen off Ushant on 4 August and was under repairs at Portsmouth until 28 December.

A landing party from Faulknor went ashore on 16 April to inspect the wreck of the beached German destroyer Z19 Hermann Künne to search for useful documents and to assess her condition.

On 4 May, Faulknor rescued 52 survivors from the Polish destroyer Grom, which had been sunk by German bombers and recovered the bodies of 60 more crewmen.

[15] The repairs were completed on 12 June and a week later, she escorted the battlecruiser Hood and the aircraft carrier Ark Royal, together with her sisters Fearless and Foxhound and the destroyer Escapade, from Scapa Flow to Gibraltar where they formed Force H.[16][17] In early July, Faulknor screened the larger British ships during the Attack on Mers-el-Kébir, in French Algeria.

[20] On 21 November, Faulknor, together with the light cruiser Despatch and Forester, intercepted the Vichy French blockade runner MV Charles Plumier and escorted her to Gibraltar.

The ship escorted Force F to Malta during Operation Collar later in the month and participated in the inconclusive Battle of Cape Spartivento on 27 November.

Faulknor rescued four survivors from the oil tanker SS British Premier on 3 February after they had been at sea for 41 days.

Their stay in Freetown did not last long as they were ordered to escort Convoy SL 67 and the battleship Malaya en route back to Gibraltar in late February.

[23] On 2–4 April, the ship led the escorts for Ark Royal as she flew off more fighters bound for Malta and repeated the mission three weeks later.

This was part of Operation Tiger which included a supply convoy taking tanks to the Middle East and the transfer of warships.

[25] Later that month, she participated in Operation Splice, another Club Run in which the carriers Ark Royal and Furious flew off fighters for Malta.

In late June, Faulknor screened Ark Royal and Furious as they flew off more fighters for Malta in Operation Railway.

[27] During a Malta supply convoy (Operation Substance), the ship went to the assistance of Fearless on 23 July, after she had been crippled and set afire by Italian torpedo-bombers, but she could not be safely towed back to Gibraltar and had to be sunk by Forester's torpedoes.

As the dockyard lacked the spare parts and the heavy lifting gear necessary, Faulknor was ordered home for a complete refit.

[28] Faulknor was assigned to the Home Fleet at Scapa Flow after the completion of her refit, and led the escort for the battleship Duke of York as she ferried Prime Minister Winston Churchill to meet with the U.S. president Franklin D. Roosevelt in the Atlantic Conference in mid-December.

Faulknor and Foresight suffered weather damage en route, and were forced to break off and seek refuge in the Azores, Portugal, before returning to Scapa Flow on 23 December.

After escorting her to Seidisfjord, Iceland, Faulknor rejoined the covering force on 9 March, shortly before it turned back for Scapa Flow.

[31] On 1 April Faulknor led a force of five other destroyers that were to escort ten Norwegian merchant ships attempting to reach Britain from Sweden via the Skagerrak.

In June 1943 Faulknor rejoined the 8th Destroyer Flotilla for Fleet duties in the Mediterranean, arriving at Alexandria on 5 July to support the Allied invasion of Sicily (Operation Husky).

She served as part of the screen for the covering force in the Ionian Sea (two aircraft carriers, three battleships, and four cruisers with 17 other Allied destroyers).

She was then detached with other destroyers to screen ships escorting the Italian Fleet to Alexandria via Malta, and then was transferred to the Eastern Mediterranean to support Allied operations in the Dodecanese Campaign.

In December Faulknor supported military operations on the west coast of Italy, escorting the landing ships Royal Ulsterman and Princess Beatrix with No.

Montgomery's insistence that the ship approach the beach as close as possible led to her running aground on a sandbank and she had to wait for the next high tide before being refloated with the aid of a tug.

Montgomery had persistently ordered the destroyer closer to shore, resulting in damage to the Sonar sensor which was situated under the hull.