The activity of the Holy See in favor of peace has developed throughout History. This work focuses on the work developed by Pope Benedict XVI in this matter. The first part refers to the pacification activity carried out by Benedict XVI through diplomatic relations, and other international activities such as mediation, good offices and international arbitration, although the brevity of his pontificate only allowed him to continue with the diplomatic relations and the signing of international agreements with the States. The second part focuses on the many appeals for peace that Benedict XVI has made in many occasions during his pontificate, with the Diplomatic Corps, the ambassadors of the different States, the Heads of State, receiving the bishops in ad limina visit, or during the Angelus prayer in St. Peter’s Square. This work has been done inside the Proyecto I+D+I DER2015-65840-R (MINECO/FEDER) “Diversidad y Convivencia: los derechos humanos como guía de acción”, del Ministerio de Economía y Competitividad y el Fondo Europeo de Desarrollo Regional.