The apparel industry of Bangladesh has been the leading export division and the preeminent source of foreign exchange. However, these industries are still confronting obstacles such as insufficient productivity, poor quality, higher defects rate which is reducing its output to a significant extent. Minimization of defects by identifying the causes in various sections of these industries can significantly improve its productivity. This study emphasizes on identifying the root causes of sewing defects in an apparel firm and proposed auspicious corrective actions to reduce these defects. This study is carried out at Fakir Apparels Limited to minimize the defects rate in its sewing section. Pareto analysis has been performed to identify the most significant one among all the defects in two production lines and root causes of these defects have been analyzed by the cause-effect diagram. Moreover, a Plan-Do-Check-Act (PDCA) Cycle has been designed to establish the corrective actions based on the root cause analysis. Finally, Technique for Order Preference by Similarity to Ideal Solution (TOPSIS), a multi criteria decision making (MCDM) technique has been used to rank and recommend different managerial decisions based on their priority and impact. The outcome of this study may bring significant changes in the sewing section of the apparel firm in terms of productivity and effectiveness.