The1H-NMR spectra of liquid binary mixtures N-methylformamide (NMF) - N, N-dimethylformamide (DMF), were recorded at 298 K within nearly the whole range of mixed solvent compositions. From these data were found the values of the spectral structural parameter, ΔΔ(NMF - DMF). The viscosities (η12) of the mixed solvents were measured at 298.15 K, as well as the relative permittivities (ϵ12) and the surface tensions (σ12) at 291.15 K, 298.15 K and 303.15 K. From all these data their deviations from ideality were calculated. Additionally, the temperature coefficients of relative permittivity, α12=1/α12[dϵ12/d(1/T)] and temperature coefficients of surface tensions, γ12=-(σ12/dT), were found. These quantities, as a function of a mole fraction, deviate very little from their molar values, indicating that the mixtures of NMF - DMF can be regarded as almost ideal.