Tavčar was born into a poor peasant family in the Carniolan village of Poljane near Škofja Loka in what was then the Austrian Empire and is now in Slovenia. He started schooling in his home village and continued in Ljubljana from where he was expelled for reasons of discipline. For a while he attended secondary school in Novo mesto and eventually returned to Ljubljana. In 1871 he began studying law at Vienna University. He began his political career in the Provincial Assembly of the Duchy of Carniola, where he formed the core of a radical group of Slovene liberals together with Ivan Hribar. He became one of the leading members of the National Progressive Party and long served as the chief editor of the party journal Slovenski narod, succeeding Josip Jurčič. Between 1901 and 1907 he was member of the Austrian Parliament. In 1911, he succeeded Ivan Hribar as mayor of Ljubljana.
He remained in office until 1921, when he withdrew from public life after being diagnosed with cancer of the intestine. He spent his last years on his estate in Visoko near Škofja Loka.
He was married to Franja Tavčar, a leading figure in the Slovene women associations at the time. The couple was the center of the social life in Ljubljana. They were both active in many organizations. Tavčar was very keen in sport and promoted cycling and athletics. He was one of the founders of the Sokol movement in the Slovene Lands.