[2] The U-class were War Emergency Programme destroyers, intended for general duties, including use as anti-submarine escort, and were to be suitable for mass-production.

[18][19][20] Undine returned to the Mediterranean with the rest of the 25th Flotilla by the end of June,[17] carrying out bombardments against targets on the Adriatic coast in September 1944.

[17][21] Undine was refitted at Chatham Dockyard from 25 September to 18 November 1944, before being sent (still as part of the 25th Flotilla) to join the British Pacific Fleet, reaching Trincomalee in Ceylon (now Sri Lanka) in December that year.

[17][20][22] On 4 January 1945, Undine took part in Operation Lentil, a strike by aircraft from the British carriers Indomitable, Indefatigable and Victorious against oil installations at Pangkalan Brandan, Sumatra.

[25][26] In March–April 1945, the British Pacific Fleet carried out a series of attacks against Japanese airfields in the Sakishima Gunto, in support of Operation Iceberg, the American invasion of Okinawa.

[28][29] In July–August 1945, the British Pacific Fleet made a series of attacks against the Japanese Home islands in conjunction with the US Navy, with Undine again operating as part of the 25th Destroyer Flotilla.

[30][31] On the night of 29/30 July, Undine, together with the destroyers Urania and Ulysses escorted King George V when she shelled factories producing aircraft propellers near Hamamatsu.

[17][35] From 1952 to 1953 she was converted into a Type 15 fast anti-submarine frigate, by Alexander Stephen and Sons at their Glasgow shipyard,[17] being allocated the new pennant number F141.

[40] On 27 October 1958, the 6th Frigate Squadron, including Undine, was off Ushant on passage from Portland to Gibraltar, when she suffered a loss of power, and while trying to turn out of line was hit by sister ship Ulysses.

[43] While Undine recommissioned back into the 6th Frigate Squadron in April 1960, she suffered defects that would require docking for rectification, which would prevent her from meeting the ship's programme of operational deployments.

[44][45] Undine was put on the Disposal List in September 1961, and arrived at the Newport, Wales of shipbreaker John Cashmore Ltd for scrapping on 12 November 1965.