Abstract—In this paper, a novel design of a compact coplanar waveguide (CPW) fed multiple-input-multiple-output (MIMO) handset antenna operating in a wide frequency range at the 5G New Radio (NR) millimeter wave (mmWave) band extending from 23.5 GHz to 41 GHz. The planar geometry results in a small, compact structure with a wide operating bandwidth, high gain, and high radiation efficiency. The utilized antenna was a single-layer surface-mounted CPW in a pin-clamp-like (PCL) structure fed with a wide ground slot. The two-element MIMO antenna consists of closely-spaced parallel elements placed λ0/16 apart from the closest edge, wherein λ0 is the free space wavelength at the 28 GHz operating frequency. A novel inverse S-shaped (IS) decoupling strip structure was used. The proposed antenna element was designed on a Rogers RT5870 substrate using CST Microwave Studio and further validated using Ansys HFSS software. The simulated frequency bandwidth was confined to (23.5-41) GHz, showing both software good agreement results. At 37 GHz, the antenna array provides a maximum simulated gain of 6.6 dBi, while its lowest was 1.5 dBi at 24 GHz, and its minimum radiation efficiency was 93% over the whole band. This array revealed excellent MIMO performance metrics, such as envelope correlation coefficient ECC, diversity gain DG, and mean effective gain MEG, of excellent results, making this array a good choice for emerging 5G communications applications.