This paper reports on an investigation of the use of expanded perlite aggregate as saturated lightweight aggregate (LWA) with respect to the mechanical and dimensional stability properties of engineered cemetitious composites (ECC). Expanded perlite aggregate was soaked in water for 24 h before its use in ECC, and replaced 10, 20, and 30% of the aggregate that was used in ECC production. The mixture proportion of a standard ECC mixture with properties that have been extensively reported in the literature is used as a reference. The properties of the specimens are compared in terms of compressive strength, flexural strength, midspan beam deflection capacity, matrix fracture toughness, drying shrinkage, autogenous shrinkage, and restrained shrinkage. The compressive strength and flexural strength of the specimens were adversely affected with presoaked LWA replacement. Midspan beam deflection capacities were partially improved, whereas matrix fracture toughness values decreased by the presoaked LWA replacement, which is beneficial with respect to the multiple cracking behavior of ECC. Presoaked LWA replacement slightly increased the drying shrinkage with respect to the reference mixture. However, the use of presoaked expanded perlite aggregate in ECC production increased the age of restrained shrinkage cracking and decreased the autogenous shrinkage capacity significantly. Therefore, together with the comparable and enhanced composite mechanical, ductility, and dimensional properties of the standard ECC mixture, the use of presoaked LWA in ECC production should improve the durability and extend the service life of structures under environmental exposure. (c) 2013 American Society of Civil Engineers.