<p>The present study explored the influence of nano-TiO₂ (NT) on the mechanical and microstructural properties of cement mortars made from ordinary Portland cement (OPC) and Portland Pozzolana cement (PPC). NT at dosages of 1, 2, and 3% by weight was added to both the OPC and PPC mortars. The compressive, split tensile, and flexural strengths of the cement mortar specimens were evaluated at curing ages of 3, 7, and 28&#xa0;days. XRD, SEM, and EDAX were used to analyze the morphology and hydration products of the NT-doped OPC and PPC cement mortar specimens. Additionally, XRD coupled with Rietveld analysis was employed to quantify the crystal phases and mineralogy of the cement mortars, and crystal structures were visualized using VESTA software to confirm the presence of specific atoms, bonds and polyhedra for both OPC and PPC. The addition of 1% NT significantly enhanced the mechanical properties of the OPC and PPC cement mortars compared with the other NT dosages. Microstructural analysis revealed that the integration of NT particles amplified the hydration products and made the mortar dense and compact by increasing the formation of calcium silicate hydrate (CSH) gel and reducing the amount of calcium hydroxide (CH) crystals. The decrease in the lattice parameters and volume and increase in the number of atoms, bonds, and polyhedra also indicate a denser compact crystal structure of both OPC and PPC modified with NT. The interatomic distances connecting Ca²⁺, Ti⁴⁺, and Si⁴⁺ with O²⁻ revealed shorter bond lengths in PPC than in OPC, and the observed variations in bond lengths (Ca²⁺–O²⁻–Ti⁴⁺ and Ca²⁺–O²⁻–Si⁴⁺) strongly suggest that the integration of NT particles with pozzolanic materials intricately influences the atomic arrangement structure and bonding geometries in cementitious materials, which was also discussed in the present work.</p>