Pascal was a member of one of the aristocratic families of Rome. He was in charge of a monastery that served pilgrims. He was elected pope in January 817. In 823, Paschal crowned Lothair I as King of Italy. He rebuilt a number of churches in Rome, including three basilicas.
According to the Liber Pontificalis, Paschal was native of Rome and son of Bonosus and Episcopa Theodora. The Liber Censuum says that Paschal was from the Massimo family, as was his predecessor Pope Stephen IV.
Pope Leo III placed Paschal in charge of the monastery of St Stephen of the Abyssinians, where his responsibilities included the care of pilgrims who came to Rome. According to early modern accounts, Leo III may have elevated Paschal as the cardinal of Santa Prassede. Goodson attributes this account to a "desire to explain the attention that the pope so lavishly and prominently paid to that church later in his career."
Paschal became pope on January 25, 817, just one day after the sudden death of Pope Stephen IV. This decision occurred before the sanction of the emperor Louis the Pious had been obtained, and was a circumstance for which it was one of his first tasks to apologize. Paschal advised the emperor that the decision had been made to avoid factional strife in Rome.
According to the Liber Pontificalis, Pope Paschal's papal legate Theodore returned with a document titled Pactum cum Pashali pontiff, in which the Emperor congratulated Paschal, recognized his sovereignty over the Papal States and guaranteed the free election of future pontiffs. This document was challenged by later historians as a forgery.
At the time of Paschal's reign, Rome was "in a tumult." "Neither the papacy nor the nobles of the ever held control for very long."
Paschal gave shelter to exiled monks from the Byzantine Empire who were persecuted for their opposition to iconoclasm, and invited mosaic artists to decorate churches in Rome. This is known because Byzantine Emperor Michael II wrote to Frankish King Louis the Pious in an attempt to stop it.
In 822, he gave the legateship over the North (Scandinavia) to Ebbo, Archbishop of Rheims. He licensed him to preach to the Danes, though Ebbo failed in three different attempts to convert them. Only later did Saint Ansgar succeed with them.
In 823, Paschal crowned and anointed Lothair I as King of Italy, which set the precedent for the pope’s right to crown kings, and to do so in Rome. Although the pope himself opposed the sovereignty of the Frankish emperors over Rome and Roman territory, high officials in the papal palace, especially Primicerius Theodore and his son-in-law Leo Nomenculator, were at the head of the party which supported the Franks. Lothair immediately made use of his new authority to side with Farfa Abbey in its lawsuit against the Roman Curia, forcing the Papal administration to return properties which had been misappropriated. The decision outraged the Roman nobility, and led to an uprising against the authority of the Roman Curia in northern Italy, led by Paschal’s former legate, Theodore, and his son Leo. The revolt was quickly suppressed, and the two leaders who were about to testify were seized at the Lateran, blinded and afterwards beheaded. Suspicious that the deaths were to cover up the involvement of the pope in the revolt, the emperor sent two commissioners to investigate. Paschal refused to submit to the authority of the imperial court, but issued an oath in which he denied all personal complicity in the crime. The commissioners returned to Aachen, and Emperor Louis let the matter drop.
Paschal rebuilt three basilicas of Rome: Santa Prassede, Santa Maria in Domnica, and Santa Cecilia in Trastevere. Paschal is credited with finding the body of Saint Cecilia in the Catacomb of Callixtus and translating it to the rebuild the basilica of Santa Cecilia in Trastevere. Paschal also undertook significant renovations on Basilica di Santa Maria Maggiore. In addition, Paschal added two oratories to Old St. Peter's Basilica, SS. Processus et Martinianus and SS. Xistus et Fabianus, which did not survive the 16th century renovation of St. Peter's.
Paschal is also sometimes credited with the renovation of Santo Stefano del Cacco in early modern sources, but this renovation was actually undertaken by Pope Paschal II.
According to Goodson, Paschal "used church-building to express the authority of the papacy as an independent state."
Only six known letters written by Paschal remain. The first (Jaffee 2546) confirms the possessions of the Territorial Abbey of Farfa. The second and third (Jaffee 2547 and Jaffee 2548) were written to a Frankish abbot prior to and after his elevation as archbishop of Vienne. The fourth (Jaffee 2550) was written to Louis the Pious. The fifth (Jaffee 2551, preserved in the Biblioteca Ambrosiana) confirms the privileges of the church of Ravenna. The last (Jaffee 2553) was written to Ebbo, the archbishop of Reims.
After Paschal's death, the Roman Curia refused him the honour of burial within St. Peter's Basilica, and he was buried in the basilica of Santa Prassede, which includes the famous Episcopa Theodora mosaic of his mother.
Paschal was later canonized, and his feast day in the Roman calendar (prior to 1963, 14 May; currently 11 February).