Densities of the water + methanol binary system and of the water + monoethanolamine + methanol ternary system were measured at atmospheric pressure over the whole range of composition at temperatures from (283.15 to 353.15) K using an Anton Paar digital vibrating glass tube densimeter. The density of water + methanol binary system increases with increasing water content. The experimental excess volume data were correlated using the Redlich-Kister equation for which optimized sets of parameters are provided at each temperature. Infinite dilution partial molar volumes have been calculated for each component and tabulated. A correlation implying specific interaction parameters adjusted for ternary excess volumes along with excess volume values of the corresponding binary systems is proposed to represent the excess volume data of the ternary system.