It is possible that in the first millennium the Christian gospel reached the attention of Koreans travelling along the Silk Road and by sea (Min Kyoung-bae 1982:36–38; K. Baker 2006:20–30; England 1996:103–4). Two arguments are advanced for a presence of ‘Nestorian’ Christianity from Persia on the peninsula in the seventh to ninth centuries, but these are not conclusive. The first is from artefacts of that date discovered in Korea (Moffett 2005:461–69). The second is from doctrinal similarities between Korean popular Buddhism and Nestorian Christianity, such as a belief in heaven and hell, salvation by grace, a compassionate female figure and expectation of a future saviour. During the period when the Mongol Empire controlled the trade routes with Europe, it is likely that Koreans encountered Russian Orthodox Christians and Franciscan missionaries, at least at the Chinese court (Moffett 1988:474–75; K. Baker 2006:61).

In the mid-sixteenth century, the Korean community on the south island of Japan (Kyushu) probably had contact with the pioneer Jesuit missionary Francis Xavier, who began his East Asian work there in 1549 (the existence of Korea was reported in Lisbon in the same year), or with later Jesuit missionaries who were based in Yamaguchi. Jesuits in Japan proposed a mission to Korea as early as 1566, and from then on different Catholic missions made repeated efforts to enter but without success. Their interest in Korea was not so much for its own sake but because the Jesuit visitors in Asia especially saw its strategic importance for the evangelisation of either China or Japan (de Medina 1991:34–38).