Belgian universities and higher education institutions welcomed thousands of students from the former Russian Empire in the late 19th and early 20th century. We are quite well informed about these students’ numbers and motives. Less research has been carried out into how they engaged in political, economic, cultural and scientific activities. This microanalytical study about the Belgian episode in the transnational life of the Polish-Jewish Alter family provides a useful starting-point. Examining the examples of the Alter brothers and sisters and several other Polish students, it becomes clear that the Brussels Université Nouvelle and other academic institutions provided a meeting place for the progressive and radical European youth. These institutions served as important nodes in a transnational network of engaged intellectuals and political activists in Belgium. An emerging leader of the secular Jewish socialist Algemeyner Yidischer Arbeter Bund in Lite, Poyln un Rusland, briefly Bund, Wiktor Alter was primarily interested in Polish politics, without, however, distancing himself from Belgian society. The youngest Alter became actively involved in local sociability during his six years’ stay in Belgium, first in Liège and later in Ghent.