He studied history at the universities of Berlin and Wrocław; then was a professor of the universities in Kraków, Lviv (where he was also the rector), Warsaw, and Poznań. He was also a deputy to the Imperial Council in Vienna (1914-1918) and to the Polish Sejm (1919-1922), and served as deputy minister of education (1918-1920). Dembiński’s most important work was his book Polska na przełomie (1913), dedicated to the Polish politics of the time of the Great Sejm, and particularly to the relations with Prussia, in which the author argued Szymon Askenazy’s points. Dembiński’s other works included O materiałach do dziejów Polski wieku XVI i XVII (1886), Papiestwo wobec upadku Polski (1893), and Źródła do dziejów drugiego i trzeciego rozbioru Polski (1902).