Synergistic solvent extraction of manganese(II) using a mixture of Cyanex 272 and Cyanex 301 from chloride solutions has been studied in the view of developing a chemical model. Slope analysis method was used for the determination of extraction stoichiometry. The equilibrium constant for the synergistic solvent extraction reaction was calculated by taking into account of the complex formation reactions between Mn(II) and chloride ions. The activity coefficients of species in the aqueous phase were estimated by applying the Bromley equation. The calculated distribution ratios of Mn(II) agreed well with the experimentally measured values.