The 5E model, an exploratory teaching model with growing popularity in the current learner-centered educational practices, aims to develop learners'' competencies. This research study hopes to evaluate the effectiveness of the 5E model in competency-based Math teaching in Vietnam. The researchers employed mixed methods with data triangulation on a 38-student Experiment Group (EG) who learned with the 5E model and a 41-student Control Group (CG) using traditional learning approaches to clarify the impact of the 5E model on the development of Math communication competency, academic performance and learning attitude among the learners. The research instruments include a pre-test, a post-test, classroom observation and a student survey. The data collected were subsequently analyzed qualitatively and quantitatively using the IBM SPSS Statistics (Version 26) predictive analytics software. The independent t-test on the two groups'' post-test scores shows that the post-treatment learning achievement of the EG was significantly better than that of the CG with the significance level 𝛼 = 0.05 and degree of freedom 𝑑𝑓 = 77, yielding the two-tailed p-value (Sig. 2-tailed) =0,001. Meanwhile, given the significance level 𝛼 = 0.05, the two-tailed p-value (Sig. 2-tailed) = 0.001 và Pearson (r) = 0.943, the paired t-test result implies that the mean test score of the EG students'' post-test was significantly higher than that in their pre-test. In addition, with the effect size at approximately 0.88, those figures suggest that applying the 5E model in the experimental process positively affected the EG student's learning performance and MCC development. The qualitative analysis with classroom observation and student survey data shows that the 5E model contributed to the students' MCC development and increasingly positive learning attitude within the EG. Apart from the research findings, the article also reveals some experiment limitations and proposes recommendations for future research.