At the age of fourteen he entered the Camaldulian Order in the monastery of Santa Maria degli Angeli, and rapidly became a leading theologian and Hellenist. In Greek literature his master was Emmanuel Chrysoloras. He became general of the order in 1431, and was a leading advocate of the primacy of the Roman Pontiff. This attitude he showed clearly when he attended the Council of Basel as legate of Pope Eugene IV, and defended the primacy of the Roman pontiff and adjured the council not to "rend asunder Christ's seamless robe".
He was next sent by the Pope to the Sigismund, Holy Roman Emperor to ask his aid for the pontiff in his efforts to end this council, which for five years had been trenching on the papal prerogatives. The Pope transferred the council from Basel to Ferrara on 18 September, 1437. In this council, and later, in that of Florence, Ambrose, by his efforts and charity toward some poor Greek bishops, greatly helped to bring about a union of the two Churches, the decree for which, 6 July, 1439, he was called on to draw up. He died soon after.
He also translated four books against the errors of the Greeks, by Manuel Kalekas, Patriarch of Constantinople, a Dominican monk (Ingolstadt, 1608), P.G., CLII, col. 13-661, a work known only through Ambrose's translation. He also translated many homilies of St. John Chrysostom; the treatise of the pseudo-Denis the Areopagite on the celestial hierarchy; St. Basil's treatise on virginity; thirty nine discourses of St. Ephrem the Syrian, and many other works of the Fathers and writers of the Greek Church. Dom Mabillon's "Letters and Orations of S. Ambrose of Camaldoli" was published at Florence, 1759. St. Ambrose is honoured by the Church on 20 November.
So strong was his hostility to some of the delegates that he described Basel as a western Babylon. He likewise supported the pope at Ferrara and Florence, and worked hard in the attempt to reconcile the Eastern and Western Churches.
Though this cause was unsuccessful, Ambrose is interesting as typical of the new humanism which was growing up within the church. Thus while among his own colleagues he seemed merely a hypocritical and arrogant priest, in his relations with his brother humanists, such as Cosimo de Medici, he appeared as the student of classical antiquities and especially of Greek theological authors.
A number of his manuscripts remain in the library of St Mark at Venice.