(YxBi1−x)2/3Cu₃Ti₄O12 (x= 0.00–0.30) ceramics were successfully prepared via the conventional solid-state method. X-ray powder diffraction confirmed the lattice constant gradually decreases with increasing Y3+ content. SEM images displayed Y3+ substitution for Bi3+ gave rise to the large abnormal grains, and the size of abnormal grains became larger with the increase of Y3+ substitution. (YxBi1−x)2/3Cu₃Ti₄O12 ceramics presented the relatively high dielectric constant of 7400 with the dielectric loss of 0.055 when x= 0.20. The analysis of complex impedance suggested the grains are semiconductive and the grain boundaries are insulating. For pure Bi2/3Cu₃Ti₄O12 ceramics, the appearance of additional low-frequency peaks in electrical modulus indicated the grain boundaries are heterogeneous. The investigation of modulus peaks fitting with Arrhenius formula implied that the low-frequency permittivity for all (YxBi1−x)2/3Cu₃Ti₄O12 ceramics was ascribed to the Maxwell–Wagner relaxation at grain boundaries. In addition, a set of clear dielectric peaks above 200∘C associated with Maxwell–Wagner relaxation can be found for all (YxBi1−x)2/3Cu₃Ti₄O12 ceramics in the temperature dependence of dielectric constant. This set of clear dielectric peaks showed a tendency to shift to higher temperatures with the increase of Y3+ substitution. Meanwhile, a tiny dielectric anomaly at room temperature was found in Y-doped Bi2/3Cu₃Ti₄O12 ceramics.(YxBi1−x)2/3Cu₃Ti₄O12 (x= 0.00–0.30) ceramics were successfully prepared via the conventional solid-state method. X-ray powder diffraction confirmed the lattice constant gradually decreases with increasing Y3+ content. SEM images displayed Y3+ substitution for Bi3+ gave rise to the large abnormal grains, and the size of abnormal grains became larger with the increase of Y3+ substitution. (YxBi1−x)2/3Cu₃Ti₄O12 ceramics presented the relatively high dielectric constant of 7400 with the dielectric loss of 0.055 when x= 0.20. The analysis of complex impedance suggested the grains are semiconductive and the grain boundaries are insulating. For pure Bi2/3Cu₃Ti₄O12 ceramics, the appearance of additional low-frequency peaks in electrical modulus indicated the grain boundaries are heterogeneous. The investigation of modulus peaks fitting with Arrhenius formula implied that the low-frequency permittivity for all (YxBi1−x)2/3Cu₃Ti₄O12 ceramics was ascribed to the Maxwell–Wagner relaxation at grain boundaries. In addition, a set of clear dielectric peaks above 200∘C associated with Maxwell–Wagner relaxation can be found for all (YxBi1−x)2/3Cu₃Ti₄O12 ceramics in the temperature dependence of dielectric constant. This set of clear dielectric peaks showed a tendency to shift to higher temperatures with the increase of Y3+ substitution. Meanwhile, a tiny dielectric anomaly at room temperature was found in Y-doped Bi2/3Cu₃Ti₄O12 ceramics.