Recent developments in the measurement of δ34S and δ33S in sulfide minerals provide a new framework to evaluate isotopic equilibrium among sulfide minerals and a new tool to investigate mineralizing processes or sources of sulfur in ore-forming systems. Isotopic equilibrium requires that values of δ34S and δ33S are highly correlated between mineral pairs and that deviations (quantified as Δ33S) from a reference mass-dependent fractionation are the same for both minerals within experimental error. In this contribution, we apply this framework for the first time to natural samples, and evaluate isotopic equilibrium among sulfide minerals from the Archean Kidd Creek volcanogenic massive sulfide deposit in Ontario, Canada. Two of eight sulfide mineral pairs showed clear isotopic disequilibrium, in agreement with interpreted paragenetic relationships; six other pairs have isotopic compositions that are consistent with equilibrium. We discuss the implications of these results for the interpretation of mineral paragenesis and sulfur isotope geothermometry at Kidd Creek. This technique offers new possibilities for evaluating sulfur isotope systematics in Archean (>2.45 Ga) ore deposits, in which the range of δ34S values is small but non-zero values of Δ33S are common.