This study is to present a parametric characterization of reaction wheel assembly (RWA) as a vibration source for quantitative prediction of operational vibrations of a receiver on which the RWA is to be installed. The parametric source characterization proposed in this paper is based on measurements of blocked forces and torques at all frequencies in a band rather than only at harmonic frequencies for each operation speed. It includes identification of structural dynamics of the RWA itself as well as source force characteristics from measurements of the blocked forces and torques. Validation of the parametric modeling of the RWA is done based on the closeness or coherence between the measurements of the power spectral density functions of the blocked forces and torques and their predictions by modeling. Additional evaluation is proposed to enhance prediction capability of the parametric model for the operational vibrations by comparing the predicted responses of a simple cantilever with measurements during actual operations of the RWA on the cantilever.