Supplementary cementitious materials (SCMs) are strongly advised as an alternative to cement to reduce its adverse environmental effects. One such SCMs is palm oil fuel ash (POFA), a waste material generated in large quantities in Southeast Asian countries, and there is insufficient data on its use in engineered cementitious composite (ECC). This study aims to optimize the properties of ECC using POFA as a cement replacement, by using 13 mixes developed by response surface methodology (RSM) with the POFA (at 20, 30, and 40 cement replacement levels) and PVA fiber (at 1, 1.5, and 2 volume fractions) as the input factors. The compressive, tensile, and flexural strengths, and tensile capacity (CS, TS, FS, and TC) were assessed. The microstructural properties were determined using Field-Emission Scanning Electron Microscopy (FESEM) and Mercury Intrusion Porosimetry (MIP). Results indicated that while the ductility and strain capacity increased with POFA, the strengths decreased by up to 51.5. However, a structural POFA-ECC could be made with up to 30 POFA and 1�5 PVA fiber. The RSM optimization revealed 27.68 POFA and 2 PVA fiber as the optimal levels of the input factors, with the experimental validation correlating with the predicted values at less than 10 error. © 2023 by the authors.