The viscosities at T = (298.15 to 338.15 K), refractive indexes, and specific conductivities of phosphoric acid in N,N-dimethylformamide + water mixtures at T = 298.15 K have been measured over the whole concentration range of components. The excess properties of the system as functions of component ratio have been calculated and fitted to the Redlich-Kister equation. Dependence of these properties on composition has been discussed.