Undoped and Zr-doped with varying concentrations (1%, 3%, and 5%) ZnO nanoparticles were successfully synthesized through auto combustion route. We have studied the structural and optical properties of synthesized samples by using X-ray diffraction (XRD), field scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy, UV–Vis spectroscopy and Raman spectroscopy. The XRD patterns for undoped and doped ZnO, reflect the various planes of wurtzite ZnO, indicating a single phase native of the samples. The peaks shifted to the low angle side followed by moderate changes of Zr assimilation in ZnO, these trends reveal the gradual expansion in crystal lattices, and this may be due to the additional interstitial incorporation of Zr. The optical absorption spectra for synthesizing samples show the absorption in the visible region. The spectra showed a red shift in the near band edge which indicates that Zr successfully incorporated into the Zn site. The FTIR spectra of undoped and doped ZnO consist of various absorption bands and change the position with the increase of Zr concentration in ZnO. Raman spectroscopy measurements showed a rapid change in the ZnO peak positions for Zr doping 3% and above, suggesting a significant disorder and changes in the ZnO structure, in support of additional interstitial Zr doping possibility.