The age of sericite from the epithermal Au-Ag-base metal mineralization of the Banska Stiavnica deposit was determined for the first time by the low-blank K/Ar method. Typical magmatic rocks of the central part of the Banska Stiavnica stratovolcano, which are associated with the ore mineralization were dated. The K/Ar ages of the older (II and III) and final (V) magmatic stages (granodiorite porphyry, quartz-diorite porphyry, biotite-amphibole andesite, rhyolite, perlite) lay in the narrow interval of values from 12.7 ± 0.4 to 11.4 ± 1.2 Ma. The age of the hydrothermal sericite according to isochron calculation is equal to 12.1 ± 0.2 Ma. These age values overlap if we take into account the analytical error margins. The proximity in age of all the magmatic events does not allow us to make age correlations of ore mineralization with specific magmatic complexes and formations. The time interval of the rock and Au-Ag-base metal mineralization formation in the central part of the Banska Stiavnica stratovolcano does not exceed 1–2 Ma and is similar to the time intervals for other comparable epithermal structures in the world, for example, Emperor (Tavua Caldera, Fiji), Sleeper (U.S.A) and others.