This paper introduces a millimeter-wave (MMW) high bandwidth antenna on low-cost flexible PET substrate for future 5G wireless networks. The antenna design consists of a rectangular patch structure having symmetrical arrangements of slots on both sides of patch. The antenna consists of a coplanar waveguide (CPW) feed with a rectangular aperture in the ground plane. The proposed antenna shows a high bandwidth of 22GHz-40GHz, which covers the Ka band (26.5-40GHz) of electromagnetic (EM) spectrum. The peak gain of antenna is 8.2dBi at 38.75GHz and the gain is above 4dBi in the complete range of operation. Antenna is well suited for future 5G wireless networks with the flexibility to incorporate on planar surfaces like windows, doors etc. or can be made a part of non-planar surfaces like uniform or casual clothing.