This study was dedicated to the synthesis of BixZn1−xO (0.00 ≤ x ≤ 0.06) nanoparticles, BZO-NPs by using the sol–gel technique. In addition, the microstructural properties, crystal imperfections and the morphology of these samples were studied. The precursors were selected to obtain stoichiometric amounts of BixZn1−xO. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and field emission scanning electron microscopy (FE-SEM) have been utilized to carry out these studies. XRD analysis revealed that these samples have a polycrystalline hexagonal wurtzite structure and nanometric dimensions. XRD-line profile analysis was used to study the microstructure and crystal defects of these nanoparticles. Crystallite size and microstrain were estimated using the Williamson–Hall method. When the Bi-content was increased, the crystallite size increased from 39.926 to 56.668 nm according to Gaussian distributions, while the microstrain decreased from 3.585 × 10−4 to 2.228 × 10−4 . The elemental composition analysis of the BZO-NPs verified the good agreement between the target materials and those experimentally obtained. Crystal imperfections, such as lattice strains, degree of lattice distortion, internal stress and dislocation density, were studied and discussed. Morphological studies showed that increasing the Bi-content improved the crystallization process, increased the crystalline agglomerations and minimized the crystal imperfections of the present BZO-NPs