The article analyzes the legal basis of the organization of the Galician Sejm, defines the process of factional organization of Ukrainian and Polish ambassadors. It is the Sejm faction that qualifies as a voluntary association of deputies of the Sejm with the aim of clear organization of work and internal communication. Given that the legal basis for the organization of the Sejm factions in the XIX century. did not exist, deputies were guided solely by practical needs – the presence of 15 votes to make a decision on the Sejm or block the resolution. In addition, the Sejm factions of Ukrainian and Polish ambassadors were formed taking into account national and political factors. At the same time, the Ukrainians were dominated by the national, which, given the small number of ambassadors, allowed to effectively oppose the Poles. For Poles, the political current was dominant, because from the first years of the Sejm's existence, 5 political currents-parties stood out among them, forming their own factions in the Sejm, which even had different views on the «Ukrainian question». It is noteworthy that during the 1860s and 1870s Ukrainian deputies joined Polish Sejm factions, and vice versa – Polish deputies of rural origin were often members of the Ukrainian Sejm faction «Russian Club», because they were guided primarily by social issues. The social affiliation of deputies had a significant influence on factional and general Sejm activities. Thus, if in the 1860s and early 1870s the Ukrainian Sejm ambassadors were dominated by representatives of the clergy, it was only at the turn of the 19th and 20th centuries. political leadership passes to the secular intelligentsia – lawyers, lawyers. Instead, among the Polish political factions, power belonged to the secular intelligentsia, who belonged to the wealthy strata of society. At the same time, it was the Ukrainian Sejm faction that differed in its clear organizational design and discipline. It is stated that for more than 50 years of the Sejm activity, no normative acts regulating the process of formation of the Sejm factions have been issued either by the central government or by the Sejm itself. The creation of Sejm factions was the competence of the deputies themselves or political groups, which were represented in the highest representative body of the region.