In this paper, the development of an all 3-D printed wide band (2-18 GHz) free-space measurement system for characterizing the complex dielectric properties of flexible as well as rigid materials was demonstrated. Each part of the setup was designed and simulated precisely to show the effect of the 3-D printed quasi-optical lenses placed in front of the wide band ridged horn antennas on the beam and radiation pattern. More than 10 parts of the setup were 3-D printed using two different 3-D printers, and the parts were assembled together with precise alignment. The method used to analytically extract the dielectric properties was explained in detail, and the analytical S-parameters were compared with experimental S-parameters for various plastic materials to verify the measurement system. Four types of commercially available materials: polyimide film (Kapton), liquid crystalline polymer sheet (LCP), ceramic-filled polytetrafluoroethylene composites (R03035), and polypropylene with different thicknesses were characterized, and obtained dielectric constant and loss tangent values were compared with the data available from the vendors.