A multi-beam antenna with a dual band operation in the 28 GHz and 31 GHz millimeter wave band is presented. The antenna has a gain of around 15 dBi in each of the three ports. The spatial footprint of the antenna is 166 mm x 123 mm x 34 mm. A waveguide lens-based approach is used to attain this gain. Cylindrical to planar wavefront transformation by a phase extraction and compensation method drives the design of the antenna. The dual band operation of the antenna aids in transmitting and receiving at two independent frequencies. Three beams originating from a shared aperture are designed to target directions of -60°, 0° and 60°. These features make the antenna a potential candidate for 5G millimeter wave applications.