Denim garment is getting popular day by day. It is highly demandable because of its versatility, comfort and durability. Different techniques of denim washing increase this demand drastically. Denim washing is the process to enhance the appearance of a garment. This enhanced appearance may be the aged look, faded look, greyer cast, or any other shade setting or resin application. The two most advanced washing techniques are; ozone wash and laser wash. The effects of ozone on environment as well as on the garment are significant and cannot be neglected because number of benefits achieved such as time saving, less energy consumption, chemical, labour cost reduction, less discharge of water and chemicals. Therefore, effects of process parameters on ozone washing for denim fabric have been investigated in this research work using three level factorial design. 33 factorial design has been designed and conducted to investigate the effect of gas concentration, time and speed on the response variables namely; Shrinkage, Tensile and Tear strength of ozone washing. The influence of individual factors and their interactions has been critically examined using software Design Expert 8.0. Prior to the analysis of variance model accuracy has been examined through various residuals plots. The study of residuals plots shown that the residuals are normally distributed and significant evidence of possible outliers was not found. So the model can be used to predicted results with 95% confidence interval. The results from the experiment suggest that two out of three factors were significant, which are speed and time that influences mainly on the tear strength of the denim garment.