A new design of MIMO antenna array for fifth generation (5G) mobile handsets is proposed in this manuscript. The configuration of the design consists of eight planar-inverted F antenna (PIFA) elements located at different corners of the smartphone printed circuit board (PCB). The employed substrate is a low-cost FR-4 laminate with an overall size of 75×150×0.8 mm3. For ease integration and design facilitation, the antenna elements and ground plane are etched on the same layer. By adding an arrow-shaped branch-strip between two adjacent PIFA elements, the impedance bandwidth and isolation characteristics are improved significantly. However, the whole antenna structure remains very simple and compact. The designed MIMO antenna provides good efficiencies and sufficient gains at the desired frequency band. Wide impedance bandwidth (S 11 ≤ −10 dB) of 3.25–3.85 GHz has been obtained for each radiator. In addition, the isolation among antenna elements is less than −15 dB at the center frequency. The calculated TARC and ECC of the antenna elements are very low over the whole band of interest. Furthermore, the proposed design exhibits sufficient performance in the presence of user-hand.