The research is devoted to the study of the traditions of polygamy in the mountain-Jewish community of the Caucasus in the XIX - early XX centuries. By the example of one case of polygamy among mountain Jews in Grozny in 1875, the author proposes to consider the existence of traditions from inside: the description and explanation by mountain Jews motivation of its preservation, the problems in polygamous families. The sources for the study are the correspondence and reports of representatives of imperial authority in the Caucasus, reflecting the spread of the tradition of polygamy among mountain Jews, the journals of the Rabbinical Commission of 1879, as well as ethnographic works explaining the origins and motives of maintaining polygamy. The presented case confirms complex intra-family relationships in polygamous families, the maintenance of the tradition of polygamy in several generations of the same family, the existence of marital relations between close relatives.