Deoxyribonucleic acid (DNA)-based polymer thin-films are characterized at microwave frequencies. The dielectric properties of the films are extracted from comparison of the propagation constants of the co-planar waveguide (CPW) lines on bare MgO substrates and the DNA-based films on MgO substrates. The insertion loss introduced by an undoped DNA-based polymer film is only 0.1 dB at 10 GHz and 0.5 dB at 30 GHz. A red-dye-doped DNA polymer film exhibited higher losses. The relative dielectric constant of the undoped DNA-based film averages to 4 at microwave frequencies, and the loss-tangent is below 0.1 up to 30 GHz. The dielectric properties of a 5% red-dye-doped DNA polymer film is compared to that of the pure DNA film. The DR1 doped DNA film exhibits 0.4-dB higher loss at 10 GHz and 0.9-dB higher loss at 30 GHz.