Two new heterocyclic monoazo disperse dyes were prepared by diazotizing 2-amino-5-methylthiazole and ethyl-1-(2-aminothiazol-4-yl)acetate and coupling with 1,2-dimethyl-indole. Characterization of the dyes was carried out by using UV-vis, FTIR, H-1-NMR and MS spectroscopic techniques. The structures of the dyes have been determined by single-crystal X-ray diffraction method. The maximum absorption peaks (lambda(max)) in the ultraviolet and visible (UV-vis) spectra of the hetarylazoindole dyes have been determined by using the density-functional (DFT method) and time-dependent density-functional (TD-DFT method) theories. Excellent agreement was found between the calculated and experimental lambda(max) values.