Secondary ion mass spectrometry (SIMS) for sulfur isotope analysis in chalcopyrite is an essential technique with exceptional spatial resolution, which enables precise constraints on mineralization mechanisms. However, the scarcity of matrix-matched chalcopyrite reference materials (RM) for SIMS hinders its accuracy and reliability. This study introduces a large-grained natural chalcopyrite RM (IGSD) for precise sulfur isotope analysis (δ34S) using SIMS and laser ablation multicollector-inductively coupled plasma mass spectrometry (LA-MC-ICPMS). Petrographic examination and electron microprobe analysis (EMPA) results confirm the homogeneity of major elements in the IGSD chalcopyrite grains. The results of in situ analysis at four SIMS laboratories and one LA-MC-ICPMS laboratory and bulk analysis confirm the homogeneity of the S isotope composition in the IGSD chalcopyrite grains. The in situ analysis result is consistent with the result of isotope ratio mass spectroscopy (IRMS), which falls within the same range of uncertainty. This supports the suitability of the IGSD chalcopyrite RM for in situ S isotope analysis. The recommended δ34S value of the IGSD chalcopyrite RM, based on IRMS, is 4.21 ± 0.23‰ (2SD, n = 30).