He became a Franciscan in 1607, and in 1617 he was made president of the Irish College at Salamanca. The next year he went to Rome and stayed there till his death.
He collected the funds for the establishment of the Irish College of St Isidore in Rome, for the education of Irish priests, opened 1625, and for fifteen years he was the rector.
A voluminous writer, his chief work was the Annales Minorum in 8 folio vols (1625-1654), re-edited in the 18th century and continued up to the year 1622; it is the classical work on Franciscan history. He published also a Bibliotheca of Franciscan writers, an edition of the works of Duns Scotus, and the first collection of the writings of St Francis of Assisi.
This article incorporates text from the public domain 1911 Encyclopędia Britannica.
As a first instalment Wadding published in 1623 at Antwerp a complete and annotated edition of the "Writings of St. Francis" was in course of preparation, Marius a Calasio, a learned Franciscan, died in Rome, leaving unpublished four large tomes of a Hebrew concordance, besides a Hebrew grammar and dictionary.
Each year Wadding kept the Feast of St. Patrick with great solemnity at St. Isidore's; and it is due to his influence, as member of the commission for the reform of the Breviary, that the festival of Ireland's Apostle was inserted on 17 March in the calendar of the Universal Church.
Wadding was not only the official representative and indefatigable agent in the Roman Curia of the archbishops and bishops of Ireland, but the Holy See took no measure of importance concerning that country without consulting him.