In this work, an ultra-wideband multiple-input multiple-output antenna on a low-cost frame retardant (Fr-4) substrate is proposed. A complex task in designing a MIMO antenna is accomplished by using the genetic algorithm. This paper develops an improved method of converting a novel compact two-element multi-band MIMO antenna into a UWB antenna using a genetic algorithm optimizer of HFSS. The length of a typical rectangular finger-like protrusion is optimized using a genetic optimizer to resonate with the proposed MIMO in UWB frequencies. To validate the outcomes of simulation, the proposed antenna model was developed on a flame retardant 4 substrate, a decent match between the measurement and simulation is observed. These designed antennas have advantages of low cost, ease of fabrication, low profile with compact design, and operating in UWB, which covers all major commercial bands. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.