The aim of this study was to investigate the effect of three synthesis parameters on the morphology and composition of nanosized binary bioactive glass particles (nBGPs) obtained through a modified Stö ber process. Syntheses were conducted by varying only one parameter at a time while keeping the other parameters constant. As already mentioned in the literature, the ammonium hydroxide volume conditioned the size of the nanoparticles. Nonagglomerated monodispersed spherical particles with a diameter between 70 and 452 nm were produced. The quantity of calcium nitrate and the moment it was introduced in the sol had a tremendous impact on the quantity of calcium inserted and on the particle morphology and aggregation state. High Ca-content particles were obtained when the calcium precursor addition time was 1 h or less after the beginning of the sol−gel reaction but at the cost of a strong aggregation. A better control on the morphology, polydispersity and dispersibility of the nBGPs was achieved when the Ca(NO 3) 2 addition time was increased up to 6 h. However, a significant decrease of the quantity of Ca 2+ inserted was also noticed. Using an intermediate (3 h) addition time, the quantity of calcium nitrate has been optimized to maximize the insertion of Ca 2+ ions inside the silica particles. Finally, an optimum initial Ca/Si atomic ratio of 2, maximizing Ca insertion while limiting the salt quantity used, was found. It led to the synthesis of particles with a molar composition of 0.9SiO 2 −0.1CaO without any side effect on the particle stability and morphological characteristics.