The objective of this research study is the in-depth evaluation of the characteristics of fiber reinforced cement-based composites containing fly ash cenospheres (FACs) as lightweight filler material. The resulting composites showed excellent mechanical properties with higher specific strength as 34.69-24.11 kPa/kgm(-3). The 28-day compressive, flexural and tensile strengths were determined in the range of 55.92-30.38 MPa, 9.29-5.38 MPa, and 3.51-1.66 MPa, respectively. The higher pozzolanic activity of FACs contributed towards the better mechanical properties even at lower density. Microstructural analyses of the composites were carried out by SEM, nitrogen adsorption, and mercury intrusion porosimetry (MIP) while TGA was used for phase identification and phase transformation studies, respectively. The results indicated that FAC is a promising material for producing strong and lightweight structural members for use in building construction which can promote sustainable development. However, excessive FACs content in the composite may lead to higher porosity due to hollow spherical shape and chemical composition of FAC particles which affects the mechanical behavior and durability of cement-based composite.