He was named Chief of Staff of the Regia Marina in 1913; he supported the signing of a naval convention between the nations of the Triple Alliance, knowing of Italy's vulnerability to seaborne threats and its dependence on its sealanes, which was concluded on October of that year.

When World War I broke out, he warned the government of Antonio Salandra that chances of Austro-Italian success against the combined force of the French and British fleets was small, and that the Regia Marina could not guarantee the safety of the Italian coast.

He resigned in October 1915 because of friction between him and the Minister of the Navy Camillo Corsi over the respective authority, and took command of the naval base of Venice.

On one hand, Thaon di Revel was "energetic and autocratic", a tireless defender of perceived allied indifference towards Italian needs and merits and of Italian independent command, and the major reason as to why a unified Mediterranean naval command never came to be (which would have led to dangerous ambiguity had a combined fleet action been imminent), which led to a less than optimal relationship with the allied navies and officers; however, he was also "thoroughly realistic", having a picture of the Adriatic theater that discouraged aggressive actions to lure out the Austrian fleet, and which led to his decision not to risk his battleships and to fight the war with smaller ships and insidious means such as the MAS (which would score several successes in the conflict, notably the sinking of the battleship SMS Szent István).

In October 1922 he was appointed Minister of the Navy in the Mussolini Cabinet; he resigned in 1925, to protest the creation of the position of Chief of the General Staff, to be assigned exclusively to Army officers.