The article presents the activities of the last landmaster of Teutonic Order in Livonia. He secularized the estates of spiritual chivalry corporation in 1561. The author pays more attention to the Kettler’s activities aimed at supporting Protestantism. The article presents data prosopographic dates oft he family Kettler (Ketteler), that speaking about his westphalian origin, which was common among the members of the Order in this period under consideration. Also the article presents the position in the Order in the final period of his history in Livonia. Also in the article presents the position of the Order in the last years of its existence in Livonia. Considered including the assembly order‘s gebitigers of April 5, 1560, reflecting the mood inside the military order before the secularization associated with both the military and political situation caused by the Livonian War, and with the religious issue.