When HMS Somali was completed, she spent most of January 1939 around Portland England carrying out torpedo and harbour exercises in severe weather. On 31st January, Somali and other British ships proceeded to Lisbon, Portugal where they engaged in a public relations visit. About 5,000 people visited Somali and the submarines beside her. Next, the squadron sailed for Gibraltar and arrived there 9th February 1939 to participate in the Home and Mediterranean Fleet exercises scheduled for later in the month. During a storm on the 14th, Somali's port bow was damaged when the passenger liner Sibajak dragged her anchor and ran into the destroyer.

On 3rd September, the 6th Destroyer Flotilla was screening British and French battle-cruisers south of Iceland. Two hours after war was declared, Somali sighted an unidentified vessel being camouflaged at sea. That ship was the 2,377 ton Hanna Böge of Hamburg, Germany. She was captured to become the first prize in the war at sea. Later in 1939, Somali began a long winter of sea patrols and convoy duty. She claimed a U-boat on 29/30th October while escorting a Norwegian convoy with HMS Tartar and HMS Ashanti. But the u-boat was not sunk. Jointly, these Tribals screened capital ships in the Atlantic and hunted the German battlecruisers Scharnhorst and Gneisenau. During the winter of 1939, Somali's engines ran smoothly but she did not escape the turbine and feed-water troubles that afflicted the other Tribals. A short stay at Smith’s Dock at Middlesbrough England rectified the problems with the machinery.

In April of 1940, Somali was with HMS Afridi and other Tribals when HMS Gurkha was lost in action. She was also one of the ships that investigated Norwegian fiords as suitable landing spots for an Allied Expeditionary Force and later participated in many of the assaults on German held positions. While coming to the aid of a sinking ship off the Norwegian coast, on 14 May 1940, Somali became the target of German bombers. Zigzagging at high speed, she avoided every bomb except the last. That bomb hit Somali at the waterline under her starboard anchor. The bulkhead was shored up and she returned to the UK for repairs only able to make 10 knots maximum.

After a refit, Somali again became the leader of the 6th Destroyer Flotilla and spent most of the winter of 1940/41 screening Home Fleet sweeps. On 7 May 1941, she captured and sank the German trawler Munchen, a prize which yielded valuable documents. Later in the month, she engaged in the pursuit of the Bismarck together with the Home Fleet. Running low on fuel forced her to return to base.

Most of June and July 1941 was spent refitting in Thornycroft’s Yard in Southampton. Her hull was strengthened, her after funnel was cut down and radar equipment installed. On the 4 August 1941, the battleship HMS Prince of Wales shipped out of Scapa Flow carrying Prime Minister Winston Churchill to his Atlantic Charter meeting in Placentia Bay, Newfoundland. The destroyer escorts included Somali but the weather was so bad, the escorts were ordered home at 25 degrees west longitude. HMS Prince of Wales continued alone at high speed.

More fleet screening followed. Somali returned to Scapa Flow alternating between Iceland and the Orkneys. Action was rarely encountered during this period. Around Christmas 1941, HMS Somali, HMS Ashanti, HMS Bedouin and HMS Eskimo took part in another raid on the Lofoten Islands but their assault was curtailed by the presence of the German air force.

From April 1942 onwards, Somali was assigned to convoy duty on the Murmansk run. By June 1942, HMS Somali, HMS Ashanti, HMS Eskimo and HMS Tartar were the last Home Fleet Tribals left. In September 1942, while escorting convoy PQ-18, a pack of U-boats located the convoy. Two merchantmen were sunk, and a short time later, HMS Ashanti sighted a u-boat running on the surface. Ashanti gave chase, at full speed firing her 4.7 inch guns as the U-boat dived. The hunt went on for two hours but the contact was lost. The Tribal was now 20 miles astern of the convoy so she steamed at full speed in order to rejoin the other ships and in doing so, ran low on fuel oil. Ashanti then changed places with Somali on the inner screen to await a favourable opportunity to refuel. At 1920hours, Somali took up Ashanti's position and was immediately hit with a torpedo. The explosion blew the torpedo tubes over the side and cut all of the port side main stringers so that the ship was only held together by the upper deck and starboard side as far as the keel. The port engine fell through the bottom of the ship and the Engine and Gear Rooms filled with water. The leaking bulkheads on either side were promptly shored up and seemed to be holding but there was no light or power except from an unreliable auxiliary diesel generator which powered the bilge pumps. The trawler, HMS Lord Middleton, took most of Somali's crew and transferred them to other ships. Of the 80 men left aboard, all were forbidden to go below except for any critical work. HMS Ashanti then took her crippled sister ship in tow, cruising at a slow 7 knots. The flat, calm sea was ideal for towing and for revealing periscope wakes. The tow wire parted company, but HMS Ashanti managed to rig up a new line and both ships continued to crawl to Akureyri. That evening, Somali's dynamo seized up so hand pumps were used for the bilge. These could not cope with the inflow of water so the Tribal's 17 degree list increased. With the donation of many electrical cables from other ships, an emergency power umbilical was rigged up from HMS Ashanti to another destroyer and the bilge pumps started operating again. Somali\'s list was reduced to 12 degrees. Power was now available for lighting and cooking as well. By the 23/24th September, Ashanti had towed Somali for 420 miles and the weather was getting worse. Somali's plates were groaning terribly. In the middle of a snow squall, observers on Ashanti's bridge saw a blue flash behind them. The towline and the electric cable had snapped and a piece of the cable was hanging over Ashanti's stern. Quickly, a 20-inch searchlight was brought to bear on the crippled ship. By now, Somali had folded in half like a hinge with bow and stern climbing skywards. For a moment, she hung motionlessly; the deck-plating then snapped and her bulkheads collapsed. Her stern capsized and sank quickly and the bow went vertically and steadily. HMS Somali (Lt. Cdr. C. Maud, RN.) was gone.  Greenland Sea. Close escort, Russia/UK convoy QP.14. Being towed by 'Ashanti', went down in bad weather, 45 men lost.

3 Sep, 1939
The German merchant Hannah Böge (2377 BRT) is captured some 350 miles south of Iceland by the British destroyer HMS Somali.