Like his father, the authorities in France also held high hopes that he would go on to occupy the same posts that his father and grandfather had held before him. Within the Sovereign Council of New France he quickly distinguished himself by his competence, integrity and innate sense of justice, and temporarily served as Attorney General. In 1719, his cousin, Pierre François de Rigaud, Marquis de Vaudreuil-Cavagnal, put his name forward to be Chief Councillor of the Sovereign Council of New France, but the Intendant, Michel Bégon de la Picardière, withdrew his support as on more than one occasion de Lotbinière had opposed attempts to interfere with decrees which the intendant wanted to have changed. De Lotbinière did not get the promotion, and in 1722, his antagonism with Bégon was again evident when the intendant wrote of him that he "thinks that he knows as much as the most diligent. He is very fond of pleasure and not too fond of work".
He had inherited the Seigneury of Lotbinière, rendering fealty and homage in 1724, and he also held land in the Seigneury of Maure. In 1717, he had started the construction of a large stone church at Lotbinière, with the help of his brother, Father Valentin, who was the parish priest there. In 1722, he was appointed general agent at Quebec for the Compagnie de l'Occident.
In 1711, he married Marie-Françoise (1693–1723), daughter of Captain François-Marie Renaud d'Avène des Meloizes and Françoise-Thérèse (b.1670), daughter of Nicholas Dupont de Neuville (1632–1716). His wife's brother, Nicolas-Marie (1696–1743), married his sister, Angélique Chartier de Lotbinière (1692–1772), and their son inherited the Marquisate de Fresnoy. Eustache and Marie-Françoise de Lotbinière were survived by five children,