Through the influence of an uncle, who had become apostolic protonotary, he, while still a young man, received various promotions from Sixtus V and Gregory XIV. By Clement VIII he was himself made protonotary and nuncio to the Frech court; Paul V also employed him in a similar capacity, afterwards raising him to the cardinalate and making him the papal legate to Bologna. On 6 August 1623, he was chosen successor to Gregory XV.
The period of his pontificate, covering as it did twenty-one years of the Thirty Years War, was an eventful one, and the ultimate result of that great struggle was largely determined by Urban's policy, which was aimed less at the restoration of Catholicism in Europe than at such an adjustemnt of the balance of parties as might best favour his own independence and strength as a temporal power in Italy. In 1626 the duchy of Urbino was incorporated into the papal dominions, and in 1627 when the direct male line of the Gonzagas in Mantua became extinct, he favoured the succession of the duke of Nevers against the claims of the Hapsburgs, whose preponderance he dreaded.
He was the last pope to extend the papal territory, and Castelfranco on the Mantuan frontier was fortified by him. In Rome he greatly strengthened the castle of Sant Angelo, removing, for the purpose of making cannons, the massive tubular girders of bronze from the portico of the Pantheon; this violation of a building which had survived from the Roman Empire led to a famous quip, quod non fecerunt barbari, fecerunt Barberini, "what the barbarians did not do, the Barbarini did." He also established an arsenal in the Vatican, as well as a manufactory of arms at Tivoli, and fortifying the harbour of civita Vecchia. It was during the pontificate of Urban that Galileo was summoned to Rome to make his great recantaion in 1633; on the other hand, the artists Poussin and Claude Lorraine were patronized by him, and it was he who brought Athanasius Kircher to Rome, and who employed Bernini to build the Palazzo Barberini, the college of the Propaganda, the Fontana del Tritone, and other prominent structures in the city.
He was the last to practice nepotism on a grand scale: various members of his family were enormously enriched by him, so that it seemed to contemporaries as if he were establishing a Barberini dynasty. He canonized many saints, among whom the most conspicuous are Ignatius Loyola, Francis Xavier, Aloysius Gonzaga, and Philip Neri. Urban VIII was a clever writer of Latin verse, and a collection of Scriptural paraphrases as well as original hymns of his composition has been frequently reprinted. His death (July 29 1644) is said to have been hastened by chagrin at the result of a war he had undertaken against the duke of Parma. He was succeeded by Innocent IX