In this research, the effect of using fly ash on sulfate resistance of concrete was investigated. Studied mixes in this work are part of a research project that investigates the influence of using binary and ternary cementitious materials on different properties of concrete. In this paper, three groups of concrete mixtures were studied; each group includes three mixes. The concrete mix proportions were adjusted to produce concrete with certain values of air content and slump. The used water / binder material ratios were 0.4, 0.5 and 0.6. Concrete samples were cured in water until testing day. After 28 days of water curing, samples were immersed in sodium sulfate solution for 6 months. The hardened concrete properties were investigated through destructive and nondestructive tests at various samples' age. The research results showed that using fly ash improved the resistance of concrete to sulfate attack. Therefore, with considerable proportions, using fly ash in concrete industry improves the performance of concrete for sulfate resistance and its durability.