AbstractIn this investigation, polyethylene terephthalate (PET) fibers obtained from the plastic bottles were used in engineered cementitious and geopolymer composites (ECC and EGC). These composites were compared with polyvinyl alcohol (PVA) and polypropylene (PP)–reinforced ECC and EGC. A total of eight mixtures (four for ECC and four for EGC) were prepared with 0% to 2% volume fraction of fibers. In each ECC and EGC series, one mixture was a control (without fibers) and a 2% volume fraction of PET, PVA, and PP fibers were added in the remaining three mixtures. The specimens prepared using these mixes were tested to failure under bending, compression, and direct tension to observe the multiple cracking and pseudo-strain-hardening (PSH) response associated with ECC. The flexural load–deflection response of fiber-reinforced ECC and EGC was observed and compared with the control mix without fibers. Besides mechanical properties, the field emission scanning electron microscopic (FESEM) images were also envisaged to observe the microstructure of the composites. It was found that the behavior of PET fiber–reinforced ECC and EGC in terms of mechanical properties was better among all combinations. PET fiber–reinforced ECC and EGC were also found competitive to PVA fiber–reinforced ECC and EGC in terms of strength and multiple cracking PSH response.