Corsini practiced law under the able direction of his uncle, Cardinal Neri Corsini.
After the death of his uncle and his father, in 1685, Corsini, now thirty-three, would have become head of the Corsini.
Instead he resigned his right of primogeniture and from Pope Innocent XI (1676–1689) he purchased, according to the custom of the time, for 30,000 scudi, a position of prelatial rank and devoted his wealth and leisure to the enlargement of the library bequeathed to him by his uncle.
Corsini's home on the Piazza Navona was the center of Rome's scholarly and artistic life.

In 1690 he was made titular Archbishop of Nicomedia and chosen nuncio to Vienna.
He did not proceed to the imperial court, because Leopold I, the Holy Roman Emperor, maintained that he had the right to select the nuncio from a list of three names furnished by the pope.

In 1696, Corsini was appointed treasurer-general and governor of the Castel Sant'Angelo.
His good fortune increased during the pontificate of Pope Clement XI (1700–1721), who employed his talents as a courtier and named him Cardinal-Priest of Santa Susanna on 17 May 1706, retaining his services as papal treasurer.

He advanced still further under Pope Benedict XIII (1724–1730), who made him Prefect of the Apostolic Signatura, a judicial branch of the Roman Curia.
He was successively appointed as the Cardinal-Priest of San Pietro in Vincoli and Cardinal-Bishop of Frascati.
Corsini practiced law under the able direction of his uncle, Cardinal Neri Corsini. After the death of his uncle and his father, in 1685, Corsini, now thirty-three, would have become head of the Corsini. Instead he resigned his right of primogeniture and from Pope Innocent XI (1676–1689) he purchased, according to the custom of the time, for 30,000 scudi, a position of prelatial rank and devoted his wealth and leisure to the enlargement of the library bequeathed to him by his uncle. Corsini's home on the Piazza Navona was the center of Rome's scholarly and artistic life.
In 1690 he was made titular Archbishop of Nicomedia and chosen nuncio to Vienna. He did not proceed to the imperial court, because Leopold I, the Holy Roman Emperor, maintained that he had the right to select the nuncio from a list of three names furnished by the pope.
In 1696, Corsini was appointed treasurer-general and governor of the Castel Sant'Angelo. His good fortune increased during the pontificate of Pope Clement XI (1700–1721), who employed his talents as a courtier and named him Cardinal-Priest of Santa Susanna on 17 May 1706, retaining his services as papal treasurer.
He advanced still further under Pope Benedict XIII (1724–1730), who made him Prefect of the Apostolic Signatura, a judicial branch of the Roman Curia. He was successively appointed as the Cardinal-Priest of San Pietro in Vincoli and Cardinal-Bishop of Frascati.
Pope Clement XII