The radio-bright Vela X component of the Vela supernova remnant (SNR) was mapped in total intensity and in polarization at 8.4 GHz with 3-arcmin resolution. Prominent filamentary structure (unrelated to the optical filaments) is seen in the polarization image and to a lesser extent in total intensity. The filaments are highly polarized, with magnetic fields directed along the filaments. They have moderate Faraday rotation (mean RM ~44 rad m^-2) and the little depolarization. Comparison with data at 5 and 2.7 GHz suggests that the overall spectral index is typical of a SNR and relatively uniform throughout the region.