This study aimed to reduce instrument packaging defects in the Central Sterile Supply Department (CSSD) using action research. Data of the instrument packs packaged by the packaging personnel at the CSSD of the authors’ institution during March to May 2023 were collected and analyzed. After identifying the problems, 2 rounds of cyclic process of “plan-action-observe-reflect” were implemented to standardize the packaging procedures and develop and improve the applicable check of standard operating procedures for the CSSD. After strictly implementing the packaging operation standards and checklists, the number of packaging defect cases dropped from 274 to 41. A significant difference was identified between the number of packaging personnel who achieved a “pass” in the assessment of 3 items for maintenance. Also, 1 item for assembly had significant differences compared with the baseline number after the first cycle (P ≤ 0.001). A significant difference was identified between the number of packaging personnel who achieved a “pass” in the assessment of 20 items for 6 components after the second cycle compared with that after the first cycle (P ≤ 0.05). Through action research methodology, strict implementation of standardized packaging procedures in the CSSD can reduce packaging defects, thereby decreasing clinical complaints and ensuring patient safety.