The name of the town was first mentioned in 1091. The town developed between Mount Uršlja gora and the western Pohorje mountain range at the confluence of the rivers Mislinja and Suhodolnica. Its history is rich and linked with the history of Stari trg where the Roman settlement of Colatio was built.

Slovenj Gradec was founded by the Counts of Andechs and it then experienced turbulent centuries passing from one owner to another while its crafts and commerce flourished. With the granting of city rights, Slovenj Gradec acquired walls, fair privileges, a court, and its own mint. Commerce and crafts were joined by the arts. The current Slovenj Gradec continues the tradition of the past; numerous exhibitions and events have brought international fame, and in 1989 the town was given the honorary title of Peace Messenger City.