Undoped and Ba-doped ZnO nanoparticles were successfully synthesized using microwave hydrothermal method. The influence of Barium concentration on physical and optical properties of ZnO nanoparticles was investigated. X-Ray Diffraction (XRD) analysis revealed that the synthesized ZnO nanoparticles are polycrystalline with hexagonal wurtzite crystal structure and their average crystallite sizes are found to vary from 20 to 21.5nm in diameter. The SEM images showed that surface morphology of the samples was influenced by the presence of Ba impurities. Ultraviolet and green emission bands around 415 and 603nm, respectively were observed in photoluminescence spectra for all samples. The FTIR spectra indicated the presence of the distinct characteristic absorption peak at 489cm(-1) for Zn-O stretching modes. Raman spectra exhibited the presence of an intense peak around 437cm(-1) followed by a peak around 586cm(-1) in the higher wave number region.