A deterministic model based on the discrete population balance equation (PBE) is used to examine the precipitation of barium sulfate nanoparticles in nonionic inverse microemulsion systems. It is shown that coagulation can have a significant effect at low initial reactants concentration. The simulation results show that a bimodal particle size distribution (PSD) observed in experimental analysis reported in the literature cannot be predicted by neglecting the coagulation effect. A coagulation kernel is proposed that takes into account the effect of interparticle forces through the Fuchs' stability ratio. The effect of electrolyte concentration on the surfactant headgroup area is also investigated. It is shown that at lower electrolyte concentration, the nucleation and growth rates increase because of higher interdroplet exchange rate. The simulation results show a qualitatively good agreement with experimental data regarding PSD prediction and dynamic evolution of mean particle diameter.