This paper presents a single-layer delay-lines based reflectarray for X-band applications. The proposed design contains an octagonal-shaped patch with T-shape delay-lines. A phase range of 500° is realized by using T-shape delay-lines. A stable phase range is achieved for TE and TM modes at 0°, 15° and 30° incident angles. An equivalent circuit model is used to investigate the resonant property of the proposed reflectarray unit element. A 21 × 21 elements reflectarray is designed, fabricated and measured on an FR-4 substrate. The proposed design provides 1-dB gain bandwidth of 18.5% and 3-dB gain bandwidth of 30%. Measured gain of 26 dBi at 10 GHz with aperture efficiency of 65% is obtained. The proposed reflectarray configuration have side-lobe-levels less than -25 dB.