De Vio was born in Gaeta, then part of the Kingdom of Naples, as Jacopo Vio.
The name Tommaso was taken as a monastic name, while the surname Cajetan derives from his native city.
 At the age of fifteen he entered the Dominican order and devoted himself to the study of the philosophy of St. Thomas Aquinas, becoming before the age of thirty a doctor of theology at Padua, and subsequently professor of metaphysics.

A public disputation at Ferrara (1494) with Pico della Mirandola made his reputation as a theologian.
He became general procurator in 1507 and general of the Dominicans a year later in 1508.
For his zeal in defending the papal rights against the 1511 Council of Pisa, in a series of works which were condemned by the Sorbonne and publicly burnt by order of King Louis XII, he obtained the bishopric of Gaeta, and in 1517 Pope Leo X made him a cardinal and archbishop of Palermo.

He appears in 1511 as a supporter of the pope against the claims of the Council of Pisa (1511-1512), called by dissident cardinals to punish Pope Julius II, who had ignored the electoral capitulations he had accepted before being elected.
 Cajetan composed in defense of his position the Tractatus de Comparatione auctoritatis Papæ et conciliorum ad invicem.
Jacques Almain answered this work, and Cajetan replied in his Apologia.
 Cajetan refused to accept Almain's argument that the Church's polity had to be similar to a lay regime, complete with limits on the ruler.
At the Fifth Lateran Council (1512–17) which Pope Julius II set up in opposition to that of Pisa, De Vio played the leading role.
During the second session of the council, in which he gave the opening oration, he brought about a decree recognizing the superiority of papal authority to that of councils.

In 1517, Leo X made him cardinal presbyter of San Sisto in Rome for his services.
In the following year he became bishop of Palermo.
He resigned as bishop of Palermo in 1519 to become bishop of Gaeta, as granted him by the Emperor Charles V for whose election De Vio had labored zealously.

In 1518 he was sent as legate to the Diet of Augsburg and to him, at the wish of the Saxon elector, was entrusted the task of examining and testing the teachings of Luther.
 According to Hilaire Belloc, "[Luther] had not been treated roughly by his opponents, the roughness had been on his side.
 But things had gone against him, and he had been made to look foolish; he had been cross-examined into denying, for instance, the authority of a General Council – which authority was the trump card to play against the Papacy."

In 1519, De Vio helped in drawing up the bill of excommunication against Luther.

De Vio was employed in several other negotiations and transactions, being as able in business as in letters.
In conjunction with Cardinal Giulio de' Medici in the conclave of 1521‑1522, he secured the election of Adrian Boeyens, bishop of Tortosa, as Adrian VI.
He retained influence under Clement VII, suffered a short term of imprisonment after the storming of Rome by the Constable of Bourbon and by Frundsberg (1527), retired to his bishopric for a few years, and, returning to Rome in 1530, assumed his old position of influence with Pope Clement, in whose behalf he wrote the decision rejecting the appeal for divorce from Catharine of Aragon made by Henry VIII of England.
Nominated by Clement VII a member of the committee of cardinals appointed to report on the "Nuremberg Recess", he recommended, in opposition to the majority, certain concessions to the Lutherans, notably the marriage of the clergy as in the Greek Church and communion in both kinds according to the decision of the council of Basel.

Cardinal De Vio died in Rome in 1534.
De Vio was born in Gaeta, then part of the Kingdom of Naples, as Jacopo Vio. The name Tommaso was taken as a monastic name, while the surname Cajetan derives from his native city.  At the age of fifteen he entered the Dominican order and devoted himself to the study of the philosophy of St. Thomas Aquinas, becoming before the age of thirty a doctor of theology at Padua, and subsequently professor of metaphysics.
A public disputation at Ferrara (1494) with Pico della Mirandola made his reputation as a theologian. He became general procurator in 1507 and general of the Dominicans a year later in 1508. For his zeal in defending the papal rights against the 1511 Council of Pisa, in a series of works which were condemned by the Sorbonne and publicly burnt by order of King Louis XII, he obtained the bishopric of Gaeta, and in 1517 Pope Leo X made him a cardinal and archbishop of Palermo.
He appears in 1511 as a supporter of the pope against the claims of the Council of Pisa (1511-1512), called by dissident cardinals to punish Pope Julius II, who had ignored the electoral capitulations he had accepted before being elected.  Cajetan composed in defense of his position the Tractatus de Comparatione auctoritatis Papæ et conciliorum ad invicem. Jacques Almain answered this work, and Cajetan replied in his Apologia.  Cajetan refused to accept Almain's argument that the Church's polity had to be similar to a lay regime, complete with limits on the ruler. At the Fifth Lateran Council (1512–17) which Pope Julius II set up in opposition to that of Pisa, De Vio played the leading role. During the second session of the council, in which he gave the opening oration, he brought about a decree recognizing the superiority of papal authority to that of councils.
In 1517, Leo X made him cardinal presbyter of San Sisto in Rome for his services. In the following year he became bishop of Palermo. He resigned as bishop of Palermo in 1519 to become bishop of Gaeta, as granted him by the Emperor Charles V for whose election De Vio had labored zealously. 
In 1518 he was sent as legate to the Diet of Augsburg and to him, at the wish of the Saxon elector, was entrusted the task of examining and testing the teachings of Luther.  According to Hilaire Belloc, "[Luther] had not been treated roughly by his opponents, the roughness had been on his side.  But things had gone against him, and he had been made to look foolish; he had been cross-examined into denying, for instance, the authority of a General Council – which authority was the trump card to play against the Papacy."
In 1519, De Vio helped in drawing up the bill of excommunication against Luther.
De Vio was employed in several other negotiations and transactions, being as able in business as in letters. In conjunction with Cardinal Giulio de' Medici in the conclave of 1521‑1522, he secured the election of Adrian Boeyens, bishop of Tortosa, as Adrian VI. He retained influence under Clement VII, suffered a short term of imprisonment after the storming of Rome by the Constable of Bourbon and by Frundsberg (1527), retired to his bishopric for a few years, and, returning to Rome in 1530, assumed his old position of influence with Pope Clement, in whose behalf he wrote the decision rejecting the appeal for divorce from Catharine of Aragon made by Henry VIII of England. Nominated by Clement VII a member of the committee of cardinals appointed to report on the "Nuremberg Recess", he recommended, in opposition to the majority, certain concessions to the Lutherans, notably the marriage of the clergy as in the Greek Church and communion in both kinds according to the decision of the council of Basel.
Cardinal De Vio died in Rome in 1534.
Thomas Cajetan