22 Apr 1943
At 03.00 hours, a British Catalina aircraft (Sqdn 190/T) attacked U-231 with 2 bombs and machine-gun fire southeast of Iceland. The boat was not damaged, but one man was lost overboard. [Obersteuermann Walter Krause]

At 12.29 hours, the boat was attacked by a British Catalina aircraft (Sqdn 190/E) with 4 bombs and again escaped undamaged.

23 Apr 1943
An unknown aircraft attacked the boat and flooded its conning tower. The boat survived and reached France on May 31 but not before being attacked again by another unknown aircraft. (Sources: Blair, vol 2, page 335)

21 May 1943
In the late evening, the boat was attacked with a bomb by an American Avenger aircraft (USN VC-9 from USS Bogue (CVE 9), pilot LtCdr Drane) near convoy ON-184. A leak in the stern trimming tank caused chlorine gas in the after battery, forcing U-231 to return to base. Because both radio transmitters had been damaged, the boat did not respond on calls by the BdU and was considered lost for a few days, until U-305 reported the mishap.

13 Jan 1944
The sinking of U-231: At 22.55 hours, the boat was attacked by the British Wellington HF168 (172 Sqdn RAF/L, pilot P/O W.N. Armstrong, RCAF) operating from the Azores after being directed to the area by a sighting report by aircraft from USS Block Island about 750 miles northeast of the Azores. The aircraft dropped three depth charges but was itself hit by AA fire, wounding the rear gunner. U-231 then crash-dived but it proved to be impossible to stay submerged, so the boat surfaced and the crew abandoned ship. The commander attempted suicide by shooting himself with a revolver into the mouth but the bullet lodged harmlessly in the back of the neck. 7 crewmen were lost, the commander and 42 survivors were picked up and taken prisoner the next day by USS Parrott and USS Bulmer and later transferred to USS Block Island.

4 recorded attacks on this boat.