The article focuses on spreading God's Mercy as one of important aspects of priesthood. In his service, a priest shows and spreads God's Mercy and continues His redemptive work. This was clearly seen in the teachings and especially the life of Blessed Rev. Michal Sopocko. According to him, priests can spread God's Mercy by preaching the Word of God, administering the sacraments and being spiritual leaders of the faithful. Rev. M. Sopocko felt very strongly his vocation as a proponent of God's Mercy and popularizer of suchlike attitudes among priests and other people in the world. He considered God's Mercy as the source of his own vocation as a priest. His meeting St. Sister Faustine was a sign of a special assignment given to him by God.