This paper deals with the densities of aqueous solutions of N-methylacetamide (NMA) in the range of concentrations x (starting from 0.0095 to 0.699) at T = 278.15, 288.15, 298.15, 308.15, 323.15, and 333.15 K and p = 10, 25, 50, 75, and 100 MPa. A modified Tate equation was used to correlate the experimental density data. The obtained absolute average deviation between the densities measured and calculated by the Tate equation was about 0.02%. The volumetric properties of the solution calculated from the density, such as molar isothermal compressions, K-T,K-m, and molar isobaric thermal expansions, E-p,E-m, were considered depending on the concentration, temperature, and pressure. Some volumetric characteristics were also obtained for an infinitely diluted aqueous solution of N-methylacetamide: the limiting partial molar volumes, V-2(infinity), the limiting partial molar isothermal compressions, K-T,2(infinity), and the limiting partial molar isobaric expansions, E-P,2(infinity). The results obtained are discussed taking into account the solute-solvent and solute-solute interactions. A tendency of N-methylacetamide molecules to self-associate in water was found, and increases in pressure and temperature lead to the weakening of the interaction between NMA molecules.