As the church normally organizes itself along territorial lines, and because they had the human and material resources, religious orders—some even specializing in it—undertook most missionary work, especially in the early phases. Over time a normalised church structure was gradually established in the mission area, often starting with special jurisdictions known as apostolic prefectures and apostolic variates. These developing churches eventually intended 'graduating' to regular diocesan status with a local episcopacy appointed, especially after decolonization, as the church structures often reflect the political-administrative reality.

The New Testament missionary outreach of the Christian church from the time of St Paul was extensive throughout the Roman Empire.

During the Middle Ages Christian monasteries and missionaries such as Saint Patrick, and Adalbert of Prague propagated learning and religion beyond the boundaries of the old Roman Empire. In the seventh century Gregory the Great sent missionaries, including Augustine of Canterbury, into England.