In this paper, a rectangular patch antenna that covers the band from 3.2 to 5.7 GHz to support 5G New Radio (NR) sub-6 GHz with high gain and efficiency is designed and implemented. Particle Swarm Optimization (PSO) algorithm is used to get the dimensions of the antenna and slots. The optimization goals are to reach the smallest dimensions of the antenna in the required bandwidth keeping scattering parameter at port 1 |S 11 | below −10 dB, a gain of 4 dBi or higher, and efficiency more than 90%, respectively. The resonance frequency of a microstrip patch is 4.45 GHz. PSO using the computer simulation tool (CST) software is used to design an antenna with desired frequency response and radiation characteristics for 5G New Radio (NR) sub-6 GHz. The antenna is designed over an FR-4 substrate with a noticeable reduction in cost, simplicity in design, and a small overall size of 23 × 15 mm 2 . The antenna is with the partial ground. The antenna has two parallel stubs and EL slots; the lengths of these slots control the desired bandwidth. A high agreement between the simulated and measured results is noticed.