Studies indicate that learners' cognitive style (CS), self-regulated learning (SRL), and working memory (WM) are associated with their academic performance. These studies describe the relationship of academic achievement with SRL, CS, or WM individually or pairwise relationships between SRL, CS, and WM rather than the overall relationship between academic achievement and each factor. In this study, a structural equation modelling (SEM) analysis was conducted to explore the overall theoretical relationship. We focused on academic achievements in mathematics and science (AAMS). A total of 191 sixth-grade students (male: 111, female: 80; mean age: 11.08 years, SD = 0.282) from two public elementary schools in Taiwan was selected as valid samples for this study. The findings indicated that CS, WM, and SRL individually had significant influences on AAMS, among which SRL had the largest effect, followed by WM and CS. Furthermore, we discovered that CS was significantly correlated with WM. The results of the analysis of the mediation effect demonstrated that CS both directly affected AAMS and indirectly affected AAMS through SRL. The implication of the findings and recommendations are also discussed.