In this research, ozonation of H-acid, a dye intermediate was studied in a semi batch reactor. The effect of pH and ozone dose on decolorization and degradation of H-acid was studied. The results showed that pH 11.5 was effective for color and COD removal. Both color (98.7%) and COD (87.8%) could be removed by 30 min of ozonation at an ozone dose of 4.33 mg/l. Oxidation and cleavage of substituent groups were evidenced by the release of nitrate and sulphate during ozonation. The study also showed that the O-3/Fe2+ ion influenced the ozonation efficiency of H-acid. Treatment with O-3/H2O2 did not enhance color and COD removal. Acetic acid and oxalic acid were identified as the major oxidation products. The ozonation reaction followed a pseudo first order kinetics. Increase in the biodegradability as measured by the BOD5/COD ratio was observed after ozonation. The study revealed that ozonation of dye intermediate is a viable technique for wastewater treatment.