The date of Patrick's death is uncertain, but his legacy is clearly recognizable. Within a half-century of his death, the entire island had converted to the Catholic faith and their ties to Rome were solidified: "Their conversion was far from being virtually instantaneous, as later legends would suggest; but it was unusually rapid, unusually thorough, and above all peaceful. No tradition with any color of historical reliability speaks of martyrdom in connection with the conversion of Ireland."

The Irish founded monasteries and convents throughout the island and lived strict, organized lifestyles that embraced ascetical practices. They focused on reading, writing, and copying manuscripts, and their work helped to ensure the survival of ancient Greco-Roman literature and culture. Saint Patrick's work also created a generation of missionaries who regularly sailed to Scotland, Wales, and the Continent in order to spread the Faith. Saint Columba (521-597) founded the monastery at Iona and evangelized in Scotland; Saint Columbanus (543-615), along with twelve companions, traveled to the Continent and introduced private and frequent auricular confession; and Saint Brendan (484-577) sailed to Iceland and possibly even North America.