The main subject of the presented research is to investigate the dielectric properties of BaBi1.8Ln0.2Nb2O9 (Ln = Ce, Gd) ceramics prepared by conventional solid state reaction route. The materials were examined using XRD and FT-IR methods. Moreover, the AC conductivity, dielectric constant and dielectric loss of the ceramics were determined. X-ray diffraction confirmed that all these compounds crystallize in an orthorhombic structure. Fourier transform infrared spectroscopy study confirmed the presence of two characteristic vibration bands located at around 617 cm-1 and 818 cm-1 for BaBi2Nb2O9. The experimental results show that the substitution of Bi by Ce or Gd causes a decrease in Curie temperature, dielectric constant and dielectric loss.