This paper presents the effect of four dissolved inorganic salts (sodium chloride, cadmium chloride, zinc chloride, and ammonium chloride) on the enthalpy of mixing of the binary system methanol + formic acid measured at 303.15 K using an isothermal displacement calorimeter with vapor space. A significantly increasing trend in excess enthalpy values for the salt cadmium chloride, an insignificant but small increase in the excess enthalpy for the salt zinc chloride, and a smaller but similar decrease in the excess enthalpy values with the addition of sodium chloride and ammonium chloride were noticed. The experimental values of the enthalpy of mixing were fitted into a modified Redlich-Kister equation, and the deviations and parameters are reported. Importance of the solute-formic acid interaction is demonstrated by the enhanced excess enthalpy of mixing (HE) values in the positive direction with increasing salt (ammonium chloride) concentration.