She saw service in World War II, first on the side of the Allies from September 1939 to June 1940, then in the forces of Vichy France until she was scuttled in November 1942.

[2][3] While she was fitting out at Toulon, France, a compressed air tank exploded aboard her on the afternoon of 7 March 1929, seriously injuring a crewman, who was hospitalized with one arm torn off and bruises over his entire body.

In 1940, the Allies made plans to intervene in Norway to prevent the shipment of iron ore from Sweden to Germany via Narvik on the Norwegian coast.

The French submarines found limited facilities available to them at Harwich and had to rely largely on Jules Verne and spare parts sent from Cherbourg in France for repairs, some of which never were completed.

At 18:30, Jules Verne and 13 submarines, including Thétis, got underway from Brest bound for Casablanca, French Morocco, which they reached on 23 June 1940.

On that day, Thétis, Calypso, and Circé were still part of the 13th Submarine Division, based at Toulon but assigned to overseas duty at Casablanca.

[2][3] The Germans seized Thétis and handed her over to the Italians, who refloated her on 1 March 1943, with the Mario Serra Company of Genoa carrying out the salvage operation.