After completing his studies at the Séminaire de Québec, he was ordained priest in 1734 and appointed pastor of Saint-Pierre-d'Orléans, which also included duties at Saint-Laurent in L'Arbre-Sec.

After thirty-five years of ministry, he was called to the episcopate and consecrated coadjutor of Quebec, 12 July 1772, the first native of Canada to become a bishop in the Catholic Church.

He confirmed Henri-François Gravé de La Rive at Quebec, Pierre Garreau at Trois-Rivières, and Étienne Montgolfier at Montreal,[3] while he oversaw things from Saint-Pierre-d'Orléans.

In Esgly's first pastoral letter he alludes to the appointment of a coadjutor, a precaution justified by age, infirmity, and the necessity of securing a successor.

Jean-François Hubert, who was a missioner at Notre-Dame-de l’Assomption near Detroit at the time, was nominated coadjutor that same year, but the approval of the British Government was withheld till 1786.

The priests Girouard, Le Roux, and Donat, of the congregation of the Holy Ghost served there, while the Irish and Scotch Catholics of the same region were attended by the Abbé Phelan and Capuchin James Jones, who resided at Halifax.