Abstract Brittle nature of gypsum restrains its wide application in construction industry. For improvement, a novel type of composite material, gypsum‐based engineered cementitious composites (GS‐ECC), was developed using specially chosen polyethylene (PE) fibers. This study investigated the rheological and mechanical properties of GS‐ECC, that is, workability, uniaxial tensile and compressive behavior, flexural strength, etc The investigation showed that GS‐ECC possessed excellent tensile strain‐hardening behavior and saturated cracking characteristics with the average tensile strain capacity more than 5%. To explore the underlying mechanism, the microstructure of interface transition zone (ITZ) between gypsum crystals and PE fibers were investigated through the use of SEM. Single fiber pull‐out test, bending‐fracture test, and single crack tension test were conducted to investigate the mesoscopic properties from fiber/matrix interface to matrix toughness and fiber bridging capacity. This study demonstrates the feasibility of achieving strain‐hardening gypsum‐based composites by adding the PE fibers.