This paper presents Substrate Integrated Waveguide (SIW) based beam scanning antenna array utilizing a Butler Matrix (BM). The proposed beamforming network is designed utilizing Electromagnetically coupled (EMC) four elements antenna array. BM has the feature of optimal amplitude and phase imbalance at its output ports. The four-beam array demonstrates wide scanning range from -42° to +42° with a peak gain of 11.1 dBi and peak side lobe levels (SLLs) of -10.12 dB over the frequency of 27.75-28.25 GHz for 5G cellular communication applications. © 2020 IEEE.