A high selective dual band and miniaturized electromagnetic band gap (EBG) unit cell is presented in this paper. The analysis and characterization of the new cell are explained. The modified compact EBG unit cell is based on cutting two inverted U-shaped slots inside the typical mushroom-like EBG. The modified EBG has a 70% size reduction. The dual-band functionality of the structure is confirmed by applying it in a dual-notch ultra-wideband antenna (3.1–10.6 GHz), and the notch frequencies are 5.2 and 5.8 GHz. The dual-band functionality has advantages of a highly selective bandpass between them. The antenna can suppress interference frequencies in less than 100 MHz bandwidth without affecting the antenna performance in the whole bandwidth. Presented results are addressed in terms of circuit modeling, 3D full-wave simulations, and measurements.