This work studies the hydration kinetics of portland cement pastes blended with multiwalled carbon nanotubes (MWCNTs) aqueous dispersions. Anionic, cationic, and nonionic surfactants—i.e., surfactants that have different charged functional groups in their structure—were used as dispersing agents. MWCNTs in powder form were dispersed in deionized water with sodium dodecyl sulfate, cetylpyridinium chloride, and triton TX-100. Three concentrations of each surfactant (1, 10, and 100 mM) were tested, and all samples were sonicated until an adequate dispersion degree was obtained. Cement pastes blended with carbon nanotubes were prepared, and their hydration kinetics were studied using the Vicat needle and isothermal calorimetry tests. It was concluded that the effect of MWCNTs on the hydration kinetics of portland cement can be masked by the effect of surfactants used as dispersing agents for the nanotubes in the mixing water.