Bi3.15Nd0.85Ti3O12 (BNT) thin ﬁlms with different thicknesses (200, 270, 360, 450 and 540 nm) were prepared on Pt/Ti/SiO2/Si substrates by sol–gel method. The effect of film thickness on the microstructure and ferroelectric properties of BNT thin ﬁlms was investigated. All BNT thin films were consisted of a single phase of bismuth-layered perovskite structure. With increasing film thickness, grains gradually became larger, the remanent polarization (2Pr) firstly increased and then decreased, and the leakage current density showed opposite trend. The 360 nm-thick BNT ﬁlm exhibited better electrical properties with 2Pr 26 µC/cm2, coercive ﬁeld (2Ec) 220 kV/cm, dielectric constant 345 (at 1 MHz) and low leakage current density.