The denim garments, which are made with many different sewing patterns, are given the final appearance by applying industrial washing processes and these are turned into high value-added fashion products. In this study, denim fabric control performed in a textile company, washing department after weaving for one month was investigated and as a result, washing defects are examined by using statistical methods. Pareto analysis, cause and effect diagram, and P control graphs, which are statistical process control methods, were used to classify the defects seen as a result of quality control. In Pareto analysis, chemical repair (20, 52 %), blue floor (19, 86 %), chemical intensive (19, 56 %), light floor (10, 71 %), deep floor (7, 95%) are in first five places among 53 defects and account for 78, 6 % of total number of defects. Of the 53 defects encountered during the washing process, it is found that only five of these defects could be prevented during the washing process, thus reducing the total waste by about 80%. In cause and effect diagram, washing defects are divided into categories as chemical, foreground, intensity, repair, tinctorial and processual and subdimensions as causes are determined. In the Laney P control chart, all processes are determined under control.