A temperature study of the hydrazine positive ion, N2H4+, showed that the ratio of the nitrogen hyperfine splitting to the proton hyperfine splitting, |aN/aH| increased with increasing temperature. The increase in |aN/aH| was approximately 3%, while the increase in aN itself was less than 1% over the 50 °C temperature range. This effect is attributed to torsional vibration about the N—N bond and is assessed on this basis.