He entered the Sulpician Seminary at Clermont, 30 October 1769, where he studied theology, then went to the "Solitude", or Sulpician novitiate, for one year. He was appointed, in 1774, director of the seminary at Limoges, where he remained till 1791.
In consequence of the threatening aspect of affairs for Catholicism in France, Jacques-André Emery, Superior-General of the Sulpicians, deemed it prudent to found a house of their institute abroad, and at the suggestion of Antonio Dugnani, nuncio at Paris, the United States was chosen. Negotiations were opened with Bishop Carroll, recently consecrated, and after some delay Rev. Francis C. Nagot, S.S., was named first director of the projected seminary at Baltimore. With him were associated MM. Levadoux, Tessier, Gamier, and Montdésir, together with several seminarians.
Rev. M. Delavau, Canon of St. Martin of Tours, and François-René de Chateaubriand joined the party, which sailed from Saint Malo, 8 April 1791, and after a tempestuous and roundabout voyage reached Baltimore 10 July. For one year M. Levadoux, as treasurer, assisted M. Nagot in organizing the Seminary of St. Mary's, and was then sent by the latter to the Illinois mission, for which M. Emery had at first destined M. Chicosneau, deeming M. Levadoux a better administrator of temporal affairs. Empowered as vicar-general by Bishop Carroll, he took his departure for the West on 15 January 1792.
His missionary labours centred on Cahokia and Kaskaskia. The registers of the latter place bear his signature from December 1792, and he seems to have spent most of his time from 1793 to 1796 at Cahokia, though after Benedict Joseph Flaget left Fort Vincennes in 1795 he visited that post also. Meanwhile as the health of M. Nagot, superior of the Sulpicians in the United States, was failing fast, he was desirous of having M. Levadoux near him at Baltimore, that he might be ready to succeed him in office; but Bishop Carroll was no less anxious to secure his services for Detroit. The bishop's wishes prevailed, and M. Levadoux became parish priest of St. Anne's in 1796. It was he who performed the obsequies of Rev. F. X. Dufaux, S.S., missionary to the Hurons at the parish of the Assumption opposite Detroit, who died at his post 10 September 1796.
After the death of Dufaux, M. Levadoux had frequent occasion to minister to the spiritual wants of the Native Americans and of other scattered Catholics from Sandusky and Mackinaw to Fort Wayne. In 1801 M. Nagot recalled M. Levadoux to Baltimore.
In 1803 he received orders from M. Emery to return to France, where he was soon appointed superior of the Seminary of St. Flour in Auvergne, and remained there until the dispersion of the Sulpicians by Napoleon I, in 1811. When their institute was revived, in 1814, the Rev. M. Duclaux, successor of Emery, placed M. Levadoux at the head of the Seminary of Le-Puy-en-Velay.