The nanocrystalline La_0.6Pb_0.4MnO₃ thin films have been grown on (100) SrTiO₃ substrates using pulsed-laser ablation technique. The atomic force microscopy and X-ray diffraction measurements show that the films consist of single-crystalline grains of an average size of _˜17nm with c-axis perpendicular to the substrate plane. These nanocrystalline films exhibit an enhanced magnetoresistance of >100% at 1T in the vicinity of the Curie  temperature.Magnetization data suggest that grain boundaries act as tunnel barriers leading to an enhancement in the magnetoresistance.