Antonio Possevino has a secure place in the annals of Vatican diplomacy. A humanist with an excellent education, with broad range of interests organizational talents and a great commitment to the Tridentine reforms' Possevino soon attracted the attention of his superiors and the Roman Curia. In the late 1570’s he was entrusted with the delicate mission of repairing Rome’s relations with Sweden.Europe’s new divisions, which followed the religious controversy triggered off by Martin Luther, John Calvin and other reformers, were a great challenge to Papal diplomacy. The Holy See decided it was time to step up efforts to restore unity with countries which had severed their links with Rome amid the power struggles of the first decades of the 16th century. In Sweden, one of the breakaway nations, the throne passed in 1568 to John III Vasa, who was married to Catherine, a devout Catholic and daughter of the Polish king Sigismund I of the Jagiellon dynasty. The importance of maintaining a Catholic presence in Sweden was always recognized by Cardinal Stanislaw Hozjusz of Poland, who had arranged for a small party of Jesuit priests to take residence at the Swedish court and assist Catherine, incarcerated with her husband and son by the previous king. Possevino went to Sweden twice. He stayed there between 19 December 1577 and 21 May 1578, and again between 26 July and 16 August 1580. Neither of his missions was successful, yet they had a fair share of complexity and drama. It is worth reviewing that episode of diplomatic history, especially as it has interesting links with the Catholic scene in Poland.