(${\text{Y}}_x$Bi${{}_{1-}}_x{)}_{2/3}$Cu₃Ti₄${\text{O}}_{12}$ ($x=$ 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 Y${{}^3}^{+}$ content. SEM images displayed Y${{}^3}^{+}$ substitution for Bi${{}^3}^{+}$ gave rise to the large abnormal grains, and the size of abnormal grains became larger with the increase of Y${{}^3}^{+}$ substitution. (${\text{Y}}_x$Bi${{}_{1-}}_x{)}_{2/3}$Cu₃Ti₄${\text{O}}_{12}$ 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 ${\text{Bi}}_{2/3}$Cu₃Ti₄${\text{O}}_{12}$ 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 (${\text{Y}}_x$Bi${{}_{1-}}_x{)}_{2/3}$Cu₃Ti₄${\text{O}}_{12}$ ceramics was ascribed to the Maxwell–Wagner relaxation at grain boundaries. In addition, a set of clear dielectric peaks above ${200}^{\circ }$C associated with Maxwell–Wagner relaxation can be found for all (${\text{Y}}_x$Bi${{}_{1-}}_x{)}_{2/3}$Cu₃Ti₄${\text{O}}_{12}$ 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 Y${{}^3}^{+}$ substitution. Meanwhile, a tiny dielectric anomaly at room temperature was found in Y-doped ${\text{Bi}}_{2/3}$Cu₃Ti₄${\text{O}}_{12}$ ceramics.(${\text{Y}}_x$Bi${{}_{1-}}_x{)}_{2/3}$Cu₃Ti₄${\text{O}}_{12}$ ($x=$ 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 Y${{}^3}^{+}$ content. SEM images displayed Y${{}^3}^{+}$ substitution for Bi${{}^3}^{+}$ gave rise to the large abnormal grains, and the size of abnormal grains became larger with the increase of Y${{}^3}^{+}$ substitution. (${\text{Y}}_x$Bi${{}_{1-}}_x{)}_{2/3}$Cu₃Ti₄${\text{O}}_{12}$ 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 ${\text{Bi}}_{2/3}$Cu₃Ti₄${\text{O}}_{12}$ 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 (${\text{Y}}_x$Bi${{}_{1-}}_x{)}_{2/3}$Cu₃Ti₄${\text{O}}_{12}$ ceramics was ascribed to the Maxwell–Wagner relaxation at grain boundaries. In addition, a set of clear dielectric peaks above ${200}^{\circ }$C associated with Maxwell–Wagner relaxation can be found for all (${\text{Y}}_x$Bi${{}_{1-}}_x{)}_{2/3}$Cu₃Ti₄${\text{O}}_{12}$ 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 Y${{}^3}^{+}$ substitution. Meanwhile, a tiny dielectric anomaly at room temperature was found in Y-doped ${\text{Bi}}_{2/3}$Cu₃Ti₄${\text{O}}_{12}$ ceramics.