Novel miniaturized cross-coupled filter with second and third spurious responses suppression is proposed. This new filter structure is incorporated with the stepped-impedance resonator, which is beneficial for size diminution, and a proposed compact harmonic suppression cell that exhibits photonic bandgap (PBG) characteristics. When compared with a conventional cross-coupled filter, the proposed square stepped-impedance cross-coupled filter acquires more than 8% size reduction and spurious responses suppression simultaneously. Furthermore, the proposed filter performance shows almost 60-dB attenuation improvement to both second and third spurious frequencies.