The purpose of this paper is to present an integrated approach for improving the quality characteristics of the injection molded part (Honda Upper Part) being manufactured at manufacturing industry (Pakistan), where the rejection rate for Honda upper part was on ramp due to sink marks defects. The proposed integrated approach embraces the concept of Design of Experiments (Taguchi Approach) and Response surface design methodology for injection molding process optimization. The Taguchi Method (TM) was used to short list the variables that have significant effects on the sink marks in injection molded parts. Furthermore, the optimization approach of Response Surface Methodology (RSM) was utilized for the experimental research to acquire a prediction model that can be used to optimize injection molding process in terms of fine sink marks reduction. The result shows that the sink marks reduction predicted by the integration of the Taguchi Method and RSM indeed decreased from 0.0088 (Taguchi’s result) down to 0.0080 mm. The empirical results reveal that the integration of the Taguchi Method and RSM could effectively improve the quality. Basically with these experiments, we tried to open the vision of manufacturers and designers regarding the application of integrated RSM/Taguchi approach using linear cum interaction regression model with selected parametric/levels setting for the dimensional accuracy of the injection molded part, and thus contributing towards improvement in process’s reliability. The integrated approach with regression model for optimization does not only provide theoretical worth to the literature and manufacturers/designers but can also be applied to different manufacturing industries for quality parts production.