At the beginning of the 20th century, some Polish Catholic priests in Poland under Prussian rule started to promote modern social work among Polish middle-class women, and encouraged them to attend German social courses. The aim of this article is to show the contexts and trends explaining why Polish clergy chose to promote German models of modern social work among Polish women when the tension between Poles and Germans was building up. The author presents arguments indicating that the idea behind the Polish priests’ efforts to train professional staff of female Catholic activists was to provide support for implementing the principles of the encyclical Rerum novarum among working class families, especially women and children. The author uses the example of Poznań/Posen as an important city where Polish priests promoted modern social work of women. A group of female leaders from the Social Department, a new organisation that was a part of the Association of Catholic Societies for Working Women, supervised by the priests, started to work with the reception and national interpretation of German, and other models of social work. These Polish women were with a part of the patron women’s movement including Ladies of Charity of St. Vincent de Paul Society (Panie Miłosierdzia Towarzystwa św. Wincentego à Paulo) and Sodalities of Mary’s Children (Sodalicje Dzieci Marii) that did not question the leading role of the clergy and German models of social work.