An in-depth study of cementitious composites incorporating fly ash cenosphere (FAC) and varying amounts of nano titania (NT) was carried out to explore the potential usefulness of NT in formulating lightweight cementitious binders for structural and functional applications. Cement pastes with fixed weight fraction (50%) of FAC, and varying amounts of NT (1·5-4·5 wt%) were prepared, keeping a fixed water-to-binder ratio of 0·35. The resulting strength and hydration attributes as well as microstructural features were studied. The use of NT in FAC incorporated cement pastes led to strength enhancement of the resulting pastes, at the age of 28 d. A 3% addition (by binder weight) of NT was found to be the optimum for incorporating in FAC modified pastes. A more even and compacted microstructure was obtained with the incorporation of NT. FAC particles showed superior bonding and interfacial characteristics. The reduced porosity, as determined from qualitative assessment by scanning electron microscopy imaging, resulted in denser composites with the addition of NT. Improved hydration attributes and microstructural features are attributed to the accelerated pozzolanic reaction of FAC in the presence of NT and the pore-filling effect of nano particles.