A miniaturized, high out-of-band rejection bandpass filter with three transmissions zeros was proposed in this paper. Three transmission zeros can be introduced into the response of the comb-line filter by using the coupling control. By using the source/load coupling and the spurlines etched on the transmission line, the out-of-band rejection can be reduced, so that the filter can obtain better performance. A miniaturized bandpass filter is designed and fabricated. The simulation results show that the working center frequency and relative bandwidth of the filter designed in this paper are 2.12 GHz and 20%, respectively, and the return loss of the filter is better than 40 dB, insertion loss is less than 0.2 dB, and out-of-band rejection is less than 40 dB. In addition, the filter has the advantages of simple and compact structure and easy processing. The actual test results are basically consistent with the simulation ones.