This study examines the impact of 20 wt% zirconium oxide nanoparticles on the early hydration kinetics of white Portland cement by isothermal conduction calorimetry and transmission electron microscopy. The findings confirm that the nano-ZrO₂ particles do not directly participate in the chemical reactions during cement hydration; although, they do divert the normal hydration processes and accelerate the initial setting reactions. The rate of heat evolution and the extent of the exotherm associated with these reactions are reduced in the presence of nano-ZrO₂. The incorporation of nano-ZrO₂ into the cement also decreases the solubility of the silicate phases but does not compromise its capacity to release hydroxide ions. There was no observed difference in the antimicrobial activity of the nano-ZrO₂-blended and unblended cement pastes against S. aureus and E. coli; however, a modest reduction in this property was noted against P. aeruginosa for the blended cement.