The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of 2,800 to 3,200 metric horsepower (2,060 to 2,350 kW; 2,760 to 3,160 shp) for use while surfaced, two Brown, Boveri & Cie GG UB 720/8 double-acting electric motors producing a total of 750 metric horsepower (550 kW; 740 shp) for use while submerged.

From there she conducted her only war patrol in the waters off Norway, in the North Sea and towards the Arctic Circle, but found no enemy ships to target, returning to Bergen without firing a shot.

She did however manage to recover two Norwegian airmen of the British Royal Air Force, whose Mosquito aircraft had been shot down by U-804 two days before they were rescued from the sea.

On the 9 August, U-1000 was detailed to serve in the Baltic Sea against Soviet shipping, which was beginning to press into German waters as the Red Army advanced on land.

On the 31 August 1944, as she passed the East Prussian town of Pillau on her way to Reval, she struck a sea mine laid by the Royal Air Force.