The temperature dependence of the rotating frame relaxation time T1ρ for protons in powdered lithium hydrazinium sulfate, Li(N2H5)SO4, has been determined from 140 to 495 °K. These measurements indicate that the –NH2 part of the N2H5+ ion executes 180° flips about the bisectrix of the H–N–H angle with activation energy of 10.7 ± 0.5 kcal/mole. Evidence for motion of the entire N2H5+ ion with activation energy of 17.4 ± 1.1 kcal/mole was also obtained. Separate reorientation and diffusion motions of the N2H5+ ion could not be distinguished, although evidence that the N2H5+ motion detected in the T1ρ measurements includes diffusion is obtained by comparing the T1ρ results with the temperature dependence of the proton second moment.