The technique of in situ Fourier transform infrared (FTIR) absorption spectroscopy has been used to determine rotational temperatures and the extent of dissociation of N2 O in a radio‐frequency (rf) glow discharge. Measurements were made at 0.65 cm-1 resolution on 13.56‐MHz plasmas at 500 mTorr, with an input flowrate of 40 sccm, and powers of 10 and 30 W. Temperature and dissociation information estimates are based upon analysis of P branch rotational lines of the 2ν1 harmonic and ν1 +ν3 combination band of the molecule. Line intensities are corrected for instrument‐induced distortion. Under the conditions investigated, rotational temperatures are between 335 and 420 K, and dissociation ranges from 45% to 75%. Both rotational temperature and dissociation increase with rf power.