Integrated learning of STEM (science, technology, engineering, and mathematics) has become a challenge in the field of technical education. To understand the effect of STEM learning, in this study, we first identified the components of STEM in relation to bag design, then asked students to learn STEM knowledge as they designed bags. In this context, we explored how learners' creative self-efficacy (CSE) related to two types of epistemic curiosity (EC) (i.e., interest type and deprivation type) and reflected the STEM knowledge they acquired and their creative performance (i.e., novelty, utility, and aesthetics). The data were subjected to confirmatory factor analysis with structural equation modeling. The results revealed that CSE was positively related to two types of EC, and knowledge acquired was positively related to creative performance. The indirect correlates between CSE and knowledge acquired, EC and creative performance, and CSE and creative performance were positively mediated by other constructs. The implication of this research is that integrating STEM into the study of fashion design can improve students' creative performance.