We present nonlinear optical absorption properties of BaTiO3 nanoparticles of different sizes prepared by the modified polymer precursor method. Structural properties of the samples were characterized using XRD and TEM, and optical properties by UV-visible light absorption. Nonlinear optical properties of the samples were measured by the single-beam open aperture Z-scan technique using 5 ns laser pulses at 532 nm. Results show that all samples exhibit a size dependent nonlinear optical response. Optical limiting efficiency increases with grain size and has a strong dependence on the structural phase of the particles. Nonlinear optical absorption is found to be enhanced when the particles undergo a transition from the cubic to the tetragonal phase. (C) 2015 Elsevier B.V. All rights reserved.