Build was completed on 30 January 1942 and the tender cost was £440,204 which excluded items such as weapons and communications equipment supplied by the Admiralty.

After a successful Warship Week National Savings campaign in January 1942, HMS Lookout was adopted by the civil community of Burnley, Lancashire.

Gun mountings 'B' and 'X' lost two cartridge cases overboard when firing abeam, but this did not affect the outcome of the trial.

Her first attempt at a four-hour full-power trial was carried out on 21 January 1942 but was abandoned due to bad weather conditions.

Lookout was with the Home Fleet in March 1942 when the German battleship Tirpitz made ineffective attempts to intercept Arctic convoys (Operation Sportpalast).

One of Lookout's first operations took place on 4–7 March, when she was part escort to a battle squadron which included Renown, King George V and Duke of York.

The next day Lookout joined Tartar in an attack on an enemy submarine which they had sighted on the surface, but no kill was made.

Lookout was then detached with Charybdis, Somali and Lightning to assist the aircraft carrier Indomitable after she had been hit by dive bombers.

During her second patrol after Operation Pedestal, Lookout encountered a merchant ship which was identified as Luarana, an Italian vessel of about 4,000 tons.

Lookout went to action stations but the vessel was found to have been abandoned and so a skeleton crew was put on board to examine her.

When the other ships were about 10 miles away, the Luftwaffe appeared expecting to find an invasion fleet, but only found the destroyer Lookout.

[4] A few days later she was nearly hit by a glider bomb but sustained little damage and was able to continue bombardments in support of the army until 15 September, when she sailed back to Malta for repairs.

Lookout remained on bombardment and escort duties of the west coast of Italy until Victory Europe day.

Sold to BISCO in January 1948, she was taken in tow to Newport, Monmouthshire for demolition by John Cashmore and arrived at the breaker's yard on 29 February that year.