This communication presents linear and planar binomial arrays for extremely low sidelobe level (SLL) on a single substrate using series feed configuration. Binomial distribution is achieved using tapered patch width. A seven-element linear binomial array using U-shaped series feed is designed and compared with a conventional series-fed array having identical radiating elements. A conventional series-fed array provides a gain of 14.9 dBi and an SLL of −14.5 dB. However, the binomial array provides SLL of −28 dB with 12.5 dBi gain at 5.76 GHz. A planar series-fed binomial array is designed using series and corner feed lines in E- and H-planes, respectively. A <inline-formula> <tex-math notation="LaTeX">3\times3 </tex-math></inline-formula> element series-fed planar binomial array is fabricated, and the measured results agree with simulated values. It provides SLL of less than −28 dB in both E- and H-planes with 12.8 dBi gain at 5.76 GHz. Both linear and planar binomial arrays provide extremely low SLL.