The rotational spectra of two isotopes of the weakly bound complex Ar–N2O have been measured by molecular beam electric resonance spectroscopy. The following spectroscopic constants and structural parameters were derived from the observations: In the average semirigid structure, the Ar is 3.460(5) Å distant from the center of mass of N2O and 7.4°(2) to either side of a line perpendicular to the N2O axis at the center of mass. Analysis of the moments of inertia of the two isotopic species and the measured dipole moments, with a classical harmonic bender model, indicates that the equilibrium Ar–N–O angle is 87±1.5° and that the sign of the N2O dipole moment is +NNO−.