The Gift Box packaging line at PT ASD experienced recurring codification defects, particularly Missing Code defects, which affected product traceability and process reliability. Historical quality control data showed that Missing Code was the dominant defect, accounting for 426,096 units or 92.7% of the recorded codification defects. This study aims to reduce codification defects on the Gift Box packaging line through the integrated implementation of DMAIC (Define, Measure, Analyze, Improve, Control), Fault Tree Analysis (FTA), and Poka-Yoke. The research followed the DMAIC framework, with the Measure phase evaluating process capability using DPMO and Sigma Level, the Analyze phase identifying root causes through Fishbone Diagram and FTA, and the Improve phase implementing Poka-Yoke-based corrective actions. The identified root causes included product accumulation at the guide rail, improper WIP input, uniform conveyor speed settings, and photoelectric sensor misalignment. The improvement actions consisted of installing a Guide Roll, applying a transparent acrylic cover, adjusting the conveyor speed ratio from 1:1:1 to 1:1.5:2, relocating the sensor, and implementing a timer-based automatic rejector. The results showed that the initial process capability was 77,296.44 DPMO with a Sigma Level of 2.93. Following the implementation of the improvements, the DPMO decreased to 257.20 and the Sigma Level increased to 4.98 based on post-improvement data collected from March to May 2026. The findings indicate that the integration of DMAIC, FTA, and Poka-Yoke improved the stability of the Gift Box coding process by addressing root causes and reducing reliance on manual error detection.