This paper introduces a design of a flat microstrip tri-band bandpass filter that is based on the first iteration Peano fractal. The structure proposed utilizes coupled lines and a loaded a symmetric two-coupled line, which put as a potential solution for wireless communication applications. A novel bandpass filter with high selectivity and good response characteristics was designed. The tri-band filter under consideration was subjected to simulation and fabrication on a substrate made of Rogers RO4350B material. The dimensions of the proposed filter are calculated to be (0.22 × 0.23) \(\lambda_{g}^{2}\) . The results of the simulation demonstrate that the tri-band bandpass filter, as proposed, exhibits three distinct passbands located at frequencies of (2.33–2.57), (3.73–3.85), and (5.57–5.94 GHz). The insertion loss values are 0.8 dB, 1.9 dB, and 1.2 dB minimums, respectively. The simulated findings show that the suggested filter has favorable transmission and reflection characteristics, together with a notable level of out-of-band rejection. There is reasonable agreement between the measured and projected simulated findings. Several advantages attributed to this filter, including low loss, compact dimensions, and significant attenuation across the three passbands.