The motion for the new holiday was put forward by a group of MPs headed by Samo Bevk of the coalition SocDems, who argued that the holiday should pay tribute to the person who first used the term Slovenians in public.
The date for the holiday was set on 8 June because that is when Trubar is thought to have been born in 1508.
The only deputy group to vote against the new holiday was the opposition People's Party (SLS), which believes the content of the new holiday should be included in the existing Reformation Day, marked on 31 October.
Primoz Trubar (1508-1586) was a protestant reformer, who founded the Protestant Church of the Slovenian Lands.
He is most well known for writing the first two books in Slovenian, Abecedarium and Catechismus, which were published in 1550 in Tuebingen, Germany.
Trubar is also said to be the first to use the term "Slovenians" to address the nation, which was then divided into different lands of the Hapsburg empire.