BACKGROUND: Dissolution of chalcopyrite is one of the most important challenges in hydrometallurgy because it is very difficult to leach due to the passivation of its surface, whose nature is still controversial. The addition of chloride ions can catalyse copper dissolution, but when it comes to bioleaching, chloride usually cannot be applied because of its toxicity to most bioleaching bacteria. RESULTS: The current work investigated, for the first time, chalcopyrite bioleaching with Sulfolobus acidocaldarius at high concentrations of chloride [up to 1.0 mol L −1 sodium chloride (NaCl)] and 67.5 ∘ C. Copper dissolution attained 100% within 14 days in the presence of microorganisms, while only 55% was observed in the abiotic test; both tests were carried out with 1.0 mol L −1 NaCl. Raman spectroscopy of the leached chalcopyrite with S. acidocaldarius and 1.0 mol L −1 NaCl revealed the presence of elemental sulphur as a reaction product on the fifth day of the experiment; jarosite was also detected after 14 days in the same test. CONCLUSION: Because of the low ability of the archaea to oxidize ferrous ion, the redox potential of the biotic test, having 1.0 mol L −1 of chloride, remained most of the time in the range 350-420 mV, in which the leaching rate of chalcopyrite was the highest.