The infrared spectra of nitrogen-14 and 15 isotopic species of nitryl chloride and fluoride have been examined in the vapor and solid states. Assignments of two fundamentals in both halides have been changed from those proposed by earlier investigators. A band at 460 cm −1 reported earlier for the fluoride and assigned to ν 3 was shown to originate from an impurity. Thermodynamic functions and new sets of force constants from both the valence and the Urey—Bradley force fields have been calculated.