This study explores the effects of high-content fly ash and limestone filler partial replacement for portland cement and silica sand, respectively on the flexural toughness parameters of engineered cementitious composites (ECC). Various groups of mixtures having variable fly ash/portland cement ratio and different levels of limestone filler were prepared. ASTM C1609, JSCE-SF4 and the Post-Crack Strength method were employed to appraise the flexural toughness parameters of the ECC mixtures at 3, 28 and 90-d. The results show that according to ASTM C1609, JSCE-SF4 and the Post-Crack Strength method, limestone filler did not significantly affect the flexural toughness, while the flexural toughness of ECC beams decreased when the fly ash content increased. Considering deflection capacity, specimens made with a FA/OPC ratio of 1.2 without limestone filler achieved higher ductility at all curing ages. Owing to its superior crack resistance and toughness compared to normal concrete, ECC with high fly ash content and limestone filler could be a sustainable alternative construction material in diverse civil engineering applications. ECC with enhanced ductility compared to normal concrete could offer increased crack resistance, durability and better resilience.