This article was devoted to synthesis nanocrystalline Cu2O thin films using the spray pyrolysis technique, besides to study the influence of their solution molarity on crystallography, microstructure and crystal defects. X-ray diffraction analysis revealed that as-deposited Cu2O films have the amorphous nature but after their annealing at 550 K for two hours they turned to have the polycrystalline cubic structure with a preferred orientation in direction. Williamson-Hall and Scherrer methods were utilized to determine the microstructural parameters using line profile analysis of X-ray diffraction. Obtained results revealed that when the solution molarity was increased from 0.01 to 0.12 M the crystallite size increased from 28.75 to 35.12 and from 16.92 to 26.22 nm, while the microstrain was found to decrease from 2.171 × 10−3 to 0.896 × 10−3 and from 5.321 × 10−3 to 3.699 × 10−3 according to Williamson-Hall and Scherrer methods, respectively. Moreover, increasing of the solution molarity of prepared Cu2O film samples led to reduce the crystal defects, where, the lattice strain, the total internal stress, the interfacial tension and the elastic strain energy were found to decrease. Furthermore, increasing of the solution molarity led also to increase the X-ray mass-density from 6.081 to 6.099 g/cm3^.