Born in Metz, Kellermann served for a short time in his father's regiment of Hussars before entering the diplomatic service in 1791. In 1793 he again joined the army, serving chiefly under his father's command in the Alps, and rising in 1796 to the rank of chef de brigade. In the latter part of Bonaparte's celebrated Italian campaign of 1796-1797 the younger Kellermann attracted the future emperor's notice by his brilliant conduct at the forcing of the Tagliamento. He was made general of brigade immediately, and continued in Italy after the Peace of Campo Formio, being employed successively in the armies of Rome and Naples under Macdonald and Championnet.