His parents, Niccolò and Thomasina Pierozzi, were in high standing, Niccolò being a notary of the Florentine Republic.
At the age of fifteen, Antoninus applied to Bl. John Dominic, the great Italian religious reformer of the period, then at the Convent of Santa Maria Novella in Florence, for admission to the Dominican Order. But he was so small he scarcely reached above the tabletop in the office of Blessed John Dominici. To put him off, the prior told him to go home and memorize the Decrees of Gratian, a compilation of Church law. Within a year, the boy had returned, had committed the decrees to memory, and was given the habit of a Dominican.
He was the first to receive the habit for the Convent of Fiesole about to be constructed by Bl. John Dominic.
Due to the unsettled state of the Church, the order, and Italian politics, the training of the young aspirants was conducted at several different locations, including Cortona, and, for a time, the regular course of studies could not be pursued. Antoninus, nothing daunted, studied by himself. He was happily associated during these years with several future Dominican saints and beati, including Lawrence of Ripafratta, the novice master; Constantius of Fabriano; Peter Capucci; and his great friend and fellow novice, the artist, Fra Angelico.
He was given consecutively several positions in the order. While still very young, he was made prior of the Minerva in Rome (1430). He served the friars in various priories in Italy (including Cortona, Fiesole (1418-28), Naples, Gaeta, Siena, and Florence). As superior of the reformed Tuscan and Neapolitan congregations, and also as prior provincial of the whole Roman province, Antoninus zealously enforced the reforms initiated by John Dominici with a view to restoring the primitive rule. Antoninus became a distinguished master of canon law and assisted popes at their councils. There is evidence that at some point he served as a judge on the Rota. Pope Eugenius IV summoned him to attend the general Council of Florence (1439), and he assisted at all its sessions.
In 1436, he founded the famous priory of San Marco in Florence with the financial aid of Cosimo de' Medici in buildings abandoned by the Silvestrines. Under his guidance and encouragement, the San Marco's monastery became the center of Christian art. He called upon his old companion, Fra Angelico, and on the miniaturist, Fra Benedetto (Angelico's natural brother), to do the frescoes and the choir books which are still preserved there. He also ensured that an outstanding library was collected.
Bust of S. Antoninus: presso l'Oratorio dei Buonomini di S.Martino
He was consecrated bishop in March 1446.
The next year, the dying Pope Eugenius summoned Antoninus to Rome in order to receive the last sacraments from the holy bishop before dying in his arms on February 23, 1447.
He refused the cardinal`s hat on several occasions.
Because of his reputation for wisdom and ability, Antoninus was often called upon to help in public affairs, civil and ecclesiastical. Pope Nicholas V sought his advice on matters of church and state, forbade any appeal to be made to Rome from the archbishop's judgements, and declared that Antonino in his lifetime was as worthy of canonization as the dead Bernardino of Siena, whom he was about to raise to the altars.
Pius II nominated him to a commission charged with reforming the Roman court. Antoninus was the only non cardinal on this college and was chosen according to the bull, "because of his high moral valor and his greatwisdom." The Florentine government gave him important embassies on behalf of the republic and would have sent him as their representative to the emperor if illness had not prevented him from leaving Florence.
On the vigil of the feast of the Ascension, 1459, St Antoninus died among his Dominican brothers who had come to pray the office for these last days around his death bed. The saint's last words were: "Servire Deo regnare est", "to serve God is to reign." At his request, he was buried in the Church of the Priory of San Marco.
The reigning pope,Pius II, in addition to officiating at the funeral, immediately prepared the canonization proceeding. Pope Adrian VI was to pronounce the canonisation when he, himself, died. St. Antoninus was canonized the same year of the death of that last pope, 1523, by the following pope, Clementus VII.
Altar in Church of San Marco, Florence with the remains of the saint
Antoninus's life was very much intertwined with the life of Fra Angelico who also did his novitiate at Cortone two year afterAntoninus. Angelico followed Antoninus to Fiesole, then to SanMarco which later was to be rebuilt in the center of Florence with the support of the most powerful man in the city, Cosmo de Medici.
As soon as St. Antoninus was made a leader of friars he was able to work towards the reform, first as prior and then as General Vicar of the Observance, following Dominici.
For his brother friars he was a reformer. For the laity he was a confessor and was known as "angel of counsel."
Saint Antoninus founded the organization called: Buonomini de San Martino, whichwas a sort of Society of St. Vincent de Paul for poor people ofhigh social rank who were ashamed to be poor.
The charity of Antoninus had several opportunities to be exercised. The plague hit Florence in 1448 and 1449. An earthquake shook it in 1453, a cyclone in 1456 and then a famine. He could be seen with his mule loaded with some emergency supplies going through the streets of the city bringing to some rescue assistance,helping others to die in a Christian fashion.
Against usurers, Antoninus was to behave also severely. He enjoyed from the pope the title of :"Associate Judge and Apostolic Commissary specially sent by the Holy See to know all the cases ofusury on the territory of Florence"
Antoninus would not interfere in the political affairs of the republic. But in the political field also he insisted that the playing field be fair. Although citizens took a pledge to conduct secret votes, the party of the Medici was exercising bullying tactics so that people's votes would not be secret. Antoninus had often protested against this procedure to no avail. One day he posted a note on the door of the cathedral excommunicating anyone who would not use secret votes. That really got the powerful mad.He further wrote the bill with his own hand, "scripsit manupropria" because he knew that the power that be would lash outagainst the poor notary whom he would have directed to transcribe the letter. The reaction was terrible. But he prevailed.
St.Antoninus spoke publicly at the ceremonies of installation of Calixtus where many people came specifically to listen to him. What St. Antoninus spoke about was the necessity to launch another crusade against the Turks who had taken Constantinople in 1453.
Antoninus was, one more time, sent as ambassador of his republic to the installation of the new pope, Pius II, and his speech was again about the crusade, against the enemies from without, and the enemies from within.
After St. Louis Marie Grignion de Montfort (a third order dominican), St. Antoninus is the next in line in the agenda of the Dominican order to promote his cause for the elevation to the dignity of Doctor of the Church.He had written his Summa, called sometimes Summa Theologica, sometimes Summa Moralis which has still to be translated in English.
His "Confessionale volgare" the oldest is for the faithful. His "Curam illius habe", or "Medicina de la anima" in Italianis chiefly for confessors. The "Defecerunt", another type of Confessionale, appears both in Latin and Italian.