After the February Revolution of 1848 he was appointed Maritime Prefect of the 4th maritime arrondissement, where he helped restore the peace. He then became "premier conseil" at the admiralty. On 1 May 1849 Vaillant was promoted to commodore ("contre-amiral"), and on 6 August 1849 was made second in command of the 2nd Mediterranean squadron, under Alexandre Ferdinand Parseval-Deschenes.