The Kirazlı deposit, located at the center of the Biga peninsula, is the only well-documented superimposed high-sulfidation (HS) epithermal Au-Ag deposit and porphyry Cu mineralization in Turkey. Ore formation and hydrothermal alteration at the Kirazlı were developed in 3 phases from older to younger: (a) porphyry Cu, (b) late molybdenite event, and (c) epithermal Au-Ag. Superimposition features of hydrothermal alteration are recognized in QEMSCAN mineral maps, suggesting progressive overprinting by epithermal-related alteration on porphyry Cu-style alteration. The δ³⁴S isotopic composition of porphyry Cu and HS epithermal deposit ranges from – 0.31 to + 3.67 ‰, and from -1.94 to 0.1 ‰, respectively. Although magmatic input is observed in the generation of both deposits, the sudden decrease in the δ³⁴S values of the HS epithermal deposit revealed that different hydrothermal fluid sources were superimposed in a later stage. The coexistence of multiphase fluid inclusions with high salinity and vapor-rich inclusions suggests the phase separation (boiling) during the hydrothermal evolution. Low-temperature inclusions with low salinity trapped in a later stage show overprinting hydrothermal activity. The hydrogen and oxygen isotopic compositions of illite and muscovite separates from phyllic and argillic alteration zones, respectively, indicate that the ore-bearing fluids at the Kirazlı district were mainly formed by the mixing of magmatic and meteoric water. The K/Ar age of the illite within an argillic alteration is ca. 26 Ma, suggesting that the prolonged hydrothermal activity at Kirazlı continued even after the formation of the HS epithermal deposit.