This paper presents an orthomode transducer (OMT) fabricated using 3-D printing. The OMT is designed to operate at two frequency bands, with each band passing an orthogonal polarization. For one polarization the band is 17–22 GHz and the other 27–31 GHz. Both polarizations are combined into a common port with square waveguide cross section. To facilitate the measurement, two tapered waveguide transitions are designed to convert the square waveguide port to standard WR-42 and WR-28 waveguides. The OMT and the waveguide transitions are made from polymer using stereolithography based 3-D printing and a 5 μm thick copper layer is deposited on them. The experimental results of the OMT are compared with simulations and discussed.