He wrote about prehistory, Roman and medieval history (most notably its numismatics), Ottoman and Turkish documents from the region, stećci, and Bosnian Cyrillic.

In youth, he showed interest in painting and technical sciences, but because of his family's poor financial situation, he opted for the study of philosophy at the University of Zagreb which lasted three years.

[2] As a student, Truhelka worked with Izidor Kršnjavi at the Strossmayer Gallery of Old Masters and made institutions' first catalog (1885).

He was engaged in the excavation of archaeological sites, Ilyrian graves and castles on prehistoric necropolises at Glasinac, a penitentiary settlement in Donja Dolina, a prehistoric cult edifice in Gorica near Posušje, and also dug up the early Christian basilica in Zenica and warned of the phenomenon of "Bosnian churches" and their early Christian background, explored the localities in the valley of Lašva river and around Stolac, the medieval Jajce and many other medieval cities.

In the field of ethnology, he worked on an ethnographic collection and gave an overview of the national life in Bosnia and Herzegovina.

He also proposed that a grave he found on Vran mountain belongs infect to a Diva Grabovčeva, a 17th century legendary heroin and a virgin in Prozor-Rama local oral tradition, thus claiming that he confirmed the myth.

[10] At the time he was leading "Zemaljski muzej" in Sarajevo, some of scientific work and research were subordinate to the proving some of his pseudo-scientific views and attempts to find a confirmation of exaggerated assertions regarding the presence of Catholicism in Bosnia.

On the other hand, in line with the politics of the Austro-Hungarian Empire, everything related to the Serbian heritage or Serbs was systematically avoided or suppressed.