High-quality Cd0.5Zn0.5Se nanoparticles with diameters ranging from 2.6 to 4.3 nm were synthesized via intensive mechanical milling for up to 20 h. The full width at half maximum (FWHM) and broadening of the diffraction peaks increased with increasing ball milling process and later decreased. XRD pattern confirmed a dominant zinc blende phase at (x = 0.5) composition. The optical spectra of the nanoparticles exhibited an onset absorption peak at 349 nm, with maximum absorption at 290 nm. The luminescence properties of the nanoparticles at room temperature were analyzed via photoluminescence spectroscopy, revealing band-edge emission at 354 nm. Photoluminescence (PL) spectra exhibit broad emission band at the range of (380-508) nm photon energy. The PL spectrum has two distinctive shoulders at 403 and 450 nm. Band emissions of 1.74, 1.54 and 1.4 eV at longer wavelengths that were associated with the surface state were also observed. High-transmission electron microscopy (HRTEM) revealed the successful annihilation of such defects with continuous milling.