The dispersion quality of nanosilica (NS) is an essential parameter to influence and control the material characteristics of nanosilica-enhanced concrete. In this research, the dispersion quality of colloidal nanosilica in simulated concrete environments was investigated using dynamic light scattering. A concrete environment was simulated by creating a synthetic pore solution that mimicked the ionic concentration and pH value of ultrahigh-performance concrete in the fluid state. Four colloidal nanosilica samples were used, ranging in particle sizes from 5 to 75 nm, with differing solid contents and stabilizing ions. It was found that the sodium stabilized 20 nm NS sol remains dispersed at a solid concentration of 2 wt % through a variety of pH values with the inclusion of potassium ions. Calcium ions are a major contributor to the agglomeration of NS sols and only small concentrations of calcium ions can drastically affect the dispersion quality.