The museum building was built in 1860 by the architect Grigore Pongracz, and the owner of the building was the baron Naláczi Carol. Located in the central square – Bobâlna Square, the initial function of the building was that of restaurant and hotel.
Dej Municipal Museum was built in 1925. The collection is formed from pieces representing Roman inscriptions, ethnography and folklore objects, architectonic fragments, ceramic tubs for water supply, rushlights, weapons, coins. A special category is the fossil remains of mammoths: incisors, molars and bones. An interesting discovery from the museum is the monetary treasure discovered at Nireş (near Dej), formed from 30 silver coins. The existence of a salt mine (Dej salt mine) in Deja locality contributed to the development of the science and technique collection with tools specific to exploitation, such as: an old scale for weighing salt, a wooden wheelbarrow for salt transportation, a pulley for mounting the salt to the surface, oil lamps of miners, models of modern machinery.