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 AEG GU 460/8–27 double-acting electric motors producing a total of 750 metric horsepower (550 kW; 740 shp) for use while submerged.

U-202's first patrol began when she left Kiel on 17 June 1941; it passed without incident and concluded with her entry into Brest in France on 23 July after 37 days at sea.

Her third patrol, beginning on 16 October, which was also successful, saw the destruction of the British-registered Flynderborg and Gretavale northeast of Newfoundland.

Her fifth patrol produced better results, damaging the British ships Athelviscount about 600 nmi (1,100 km; 690 mi) east southeast of Halifax on 22 March 1942 and sinking Loch Don about 500 nmi (930 km; 580 mi) north northeast of Bermuda on 1 April.

On 12 June she landed four saboteurs at Amagansett, New York, on Long Island, as part of Operation Pastorius.

The boat's seventh patrol took in the northern coast of South America, leaving Brest on 6 September 1942.

U-202 took part in ten wolfpacks, namely: 'HF/DF' (radio detection equipment) of ships in the Second Support Group, (headed by the British sloop HMS Starling commanded by Captain FJ Walker, RN), detected U-202 when she transmitted a daily report at 9:30 am on the 1 June 1943.

On closing the range, Starling's lookout spotted the swirl of water where U-202 had just crash dived after identifying the approaching vessels as warships.

The six British warships eventually adopted the tactic of keeping the U-boat moving, so as to use up her reserves of battery power.

He turned Starling aside, firing depth charges at a shallow setting from the port thrower as she passed by.