This study aimed to estimate the paddy rice yield using full polarimetric air-borne X-band synthetic aperture radar (SAR) data. We analyzed X-band Pi-SAR2 data of the early maturing stage of rice crops from Osaki City, Miyagi Prefecture, Japan, which were acquired at two different incidence angles, 32° and 53°. Four-component decomposition and eigenvalue-eigenvector decomposition were applied for the data, and full polarimetric parameters were extracted. The correlation of backscattering coefficient values and the full polarimetric parameters with the paddy rice yield were examined. The contribution of volume and surface scattering and scattering entropy computed from the data obtained at incidence angle of 53° were correlated with the paddy rice yield. These parameters were sensitive to panicle biomass and hence can be possible for estimating paddy rice yield.