In this paper, we propose a double coupled-line low-pass filter design. The filter consists of two coupled lines connected end-to-end with a common point. The low-pass filter has a sharp slope response near the 3-dB frequency cutoff point, low pass band insertion loss, and compact size. The circuit analysis was performed by a coupled transmission line and a T-type equivalent circuit, and the circuit was evaluated by an electromagnetic simulator, IE3D. Two low-pass filters with 3-dB cutoff frequency at 2.45 and 5.2 GHz were designed and measured. The measured and simulated results show good agreement in the frequency range from 0.1 to 13 GHz.