In this manuscript, a single‐fed circularly polarized patch antenna is presented, which features a large bandwidth and a high out‐of‐band suppression level, simultaneously. By loading a stacked patch and etching U‐shaped slots on the driven and stacked patches respectively, a high out‐of‐band suppression level can be obtained without any extra filtering circuits. Furtherly, to widen the bandwidth of the filtering CP patch, two T‐shaped slots and a stepped via‐line‐via feeding structure are introduced. Finally, for demonstration, a prototype was fabricated and measured. The measurements indicated a large impedance bandwidth of 35.7%, an axial‐ratio bandwidth of 10.8%, a peak gain of 8.5 dBic, and a high out‐of‐band suppression level of up to 28.5 dB in stopbands.