The microwave spectra of two conformers of N,N-diethylpropionamide were recorded using a molecular beam Fourier transform microwave spectrometer operating in the frequency range 2-26.5 GHz. Hyperfine splittings arising from the N-14 quadrupole coupling effect were observed and analyzed. Fits using a rigid rotor model with centrifugal distortion correction and first-order perturbation approach for the quadrupole coupling yielded highly accurate molecular parameters and standard deviations within the measurement accuracy for both conformers. Complementary quantum chemical calculations were carried out for a conformational analysis, theoretical values of the spectroscopic constants, and the N-14 nuclear quadrupole coupling constants.