An important goal of teaching mathematics is to form and develop students’ abilities to apply mathematical knowledge to solve problems arising from real life. This goal is also associated with the evaluation of specific mathematical competencies: mathematical thinking and reasoning, inference and proof, communication, modelling, problem solving and representation, using mathematical symbols and languages, using calculation tools. Among these competencies, modelling is the capacity mentioned by educators around the world and holds an increasingly important position in many popular mathematics programs of several countries. The objective of this study is to foster students’ mathematical modelling competency through teaching sine and cosine theorems. The sample included 46 10th grade students at Phan Thanh Giang high school, Ben Tre province, Vietnam, and they were asked to solve numerous real-world problems associated with the theorems. The qualitative analysis method was used to evaluate students' performance in mathematical modelling competence. The results were found that most of the students made progress in mathematical modelling competency, from which they not only had the right motivation to learn but also supported them in realising the application of mathematics in practice.