The effects of glass cenosphere particles on the properties of fiber-reinforced cement-based composites are explored in this study. Lightweight glass cenospheres were used as fillers in the cementitious composites and incorporated in various proportions. The developed composites were evaluated for mechanical strength parameters including compressive strength, flexural strength, tensile strengths, and elastic modulus. Microstructural investigations were also carried out. The results showed that utilizing glass cenospheres up to 30% (by cement weight) leads to adequate mechanical strength where the corresponding specific strength of 28 kPa/kg m could be achieved. Microstructural analyses further revealed that increased porosity due to glass cenospheres incorporation is primarily responsible for strength loss with increasing weight fraction.