[1] The school was ceremoniously opened on 26 October 1893 and, despite concerns raised by the National Government, it immediately enrolled members of all of Bosnia and Herzegovina's religious groups: Orthodox Christians, Catholics, Muslims and Jews.

[1] The first teaching staff was formed by three teachers, including the Slovene philologist Martin Bedjanič (1855–1931), whose assigned subjects were Bosnian and Latin and who also served as he first principal, and the biologist Antun Pichler (1862–1922), who taught Natural Sciences.

[2] Besides instructions in Islam, Serbian Orthodoxy, Roman Catholicism or Judaism,[2] the compulsory subjects were Bosnian, German, Latin, Greek (or, alternatively, Classical Arabic for Muslim students),[2] Geography and History, Mathematics, Natural Sciences, Philosophical Propaedeutics, Free-Hand Drawing, Penmanship and Gymnastics.

[6] The first students included the geographer Jevto Dedijer (whose lowest grade was in Geography),[1] the poet Osman Đikić (awarded for performance[1] but later expelled for political activity)[4] and the journalist Risto Radulović.

[10] The school alumni include the historian Vladimir Ćorović, the philosopher and poet Dimitrije Mitrinović,[12] and the writer Predrag Matvejević.

[11] The Communist activist and future Prime Minister of Bosnia and Herzegovina Avdo Humo also attended the gymnasium before being evicted in November 1931 due to "committing political transgressions at school".

[15] Gimnazija Mostar presently operates under two separate secondary school curricula and in two completely mutually intelligible language varieties, Bosnian and Croatian, with sports and a few classes combined.

[15][16][17] Though it was originally intended to fully integrate subjects or at least the science ones (Biology, Chemistry, Information Technology, Mathematics and Physics),[9] the idea of unification was fiercely opposed by local politicians, especially Croat officials who felt that their national identity was being threatened.